Overview.src.html

<h1>CSS Paged Media Module Level 3</h1>

<pre class='metadata'>
Shortname: css-page
Level: 3
Status: ED
ED: http://dev.w3.org/csswg/css-page/
TR: http://www.w3.org/TR/css3-page/
Previous Version: http://www.w3.org/TR/2013/WD-css3-page-20130314/
!Issue Tracking: <a rel="issues" href="http://www.w3.org/Style/CSS/Tracker/products/13">http://www.w3.org/Style/CSS/Tracker/products/13</a>
Editor: Melinda Grant, Hewlett-Packard
Editor: Håkon Wium Lie, Opera Software
Editor: Elika J. Etemad, Mozilla
Editor: Simon Sapin, Mozilla&#44; formerly Kozea
Ignored terms: fit, fit-position
Link defaults: css-break (property) break-after, css21 (property) display, css21 (property) min-height, css21 (property) max-height, css21 (property) min-width, css21 (property) max-width, css21 (property) margin, css-content-3 (property) counter-increment, css-content-3 (property) counter-reset
Abstract: This module describes the page model that partitions a flow into pages. It builds on the <a href="http://www.w3.org/TR/CSS21/box.html">Box model module</a> and introduces and defines the page model and paged media. It adds functionality for pagination, page margins, page size and orientation, headers and footers, widows and orphans, and image orientation. Finally it extends generated content to enable page numbering and running headers / footers.
</pre>

<style type="text/css">
  #margin-values { border-collapse: collapse; }
  #margin-values td,
  #margin-values th
  {
                padding: 0.2em;
                border: thin solid black;
  }

  .property-list
  {
                border: 1px solid black;
                padding: .2em;
                margin-top: 2em;
  }

  .property-list td
  {
                border: 1px solid black;
                padding: .1em;
  }

  .RFC2119
  {
                text-transform: lowercase;
                font-style: italic
  }

  table.page-sizes
  {
                border: thin solid;
                margin-top: 1.5em;
  }
  table.page-sizes td
  {
                border: thin solid;
                padding: .5em;
  }
  table.page-sizes th
  {
                border: thin solid;
                padding: .5em;
                background: #ffffaa;
  }
</style>


<h2 id="intro">Introduction</h2>

<p>Paged media (e.g., paper, transparencies, photo album pages, pages
displayed on computer screens as printed output simulations) differ from
<a href="http://www.w3.org/TR/CSS2/media.html#continuous-media-group">continuous media</a>
in that the content of the document is split into one or more discrete
static display surfaces. To handle pages, CSS3 Paged Media describes how:</p>

<ul>
  <li><a href="#page-breaks">page breaks</a> are created and avoided;</li>
  <li>the page properties such as size, orientation, margins, border, and
  padding are specified;</li>
  <li>headers and footers are established within the page margins;</li>
  <li>content such as page counters are placed in the headers and footers; and</li>
  <li>orphans and widows can be controlled.</li>
</ul>

<p>This module defines a <a href="#page-model">page model</a> that specifies how a
document is formatted within a rectangular area, called the
<a href="#page-box-page-rule">page box</a>, that has finite width and height.

<p>Although CSS3 does not specify how user agents transfer page boxes to sheets,
it does include certain mechanisms for telling user agents about the intended
page sheet <a href="#page-size">size and orientation</a>. In the general case,
CSS3 assumes that one page box will be transferred to one surface of similar
size.</p>

<p>All properties defined in this specification also accept the
<a href="http://www.w3.org/TR/CSS21/cascade.html#value-def-inherit">inherit</a>
keyword as their value, but for readability it has not been listed explicitly.

<h2 id="page-terms">Page Terminology</h2>

<p>The following terminology and accompanying diagrams help to describe the
page model:</p>

<dl>
  <dt id="page-sheet">Page sheet</dt>
  <dd><img src="PageSheet.png" style="float: right;" alt="The corner of a page sheet with the non-printable area at the edge and printable area inside it"
  height="148" width="194">The page sheet is one surface of the physical
  medium. The illustration to the right shows a representation of the upper-left
  corner of a page sheet.</dd>

  <dt id="printable-area">Printable and non-printable areas</dt>
  <dd>The non-printable area is the area of a page sheet that a physical device such
  as a printer is not capable of marking reliably, usually due to the printer's
  paper handling mechanism. This value is printer dependent and is usually a
  small region along each edge of the page sheet. The printable area is the area
  of page sheet that a printer <em>is</em> capable of marking reliably. The size
  of the printable area is the size of the page sheet reduced by the size of the
  non-printable area. A user agent may not know the dimensions of this area for a
  particular printing device; but when its dimensions are known, user agents
  <em class="RFC2119">MAY</em> adjust the formatting of the document so that
  content falls within the printable area. How this adjustment is accomplished is
  device dependent within the constraints expressed in the sections
  <a href="#renderingpages">Rendering page boxes that do not fit a page sheet</a> and
  <a href="#content-outside-box">Content outside the page box</a>.</dd>

  <dt id="page-orientation">Page Orientation</dt>
  <dd>The page orientation is defined by comparing the length of the edges of a
  <a href="#page-box">page box</a>. The page box is a rectangle with two
  perpendicular edges called the long edge and the short edge. The length of the
  long edge is always greater than or equal to the length of the short edge. When
  the page box is square, the two edges are of the same length and either can be
  used as the long edge with the other being the short edge. This specification
  defines page orientations of ''portrait'' and ''landscape''.</dd>

  <dt id="portrait">Portrait Orientation</dt>
  <dd>A portrait page's height is greater than or equal to its width. Horizontal
  elements are parallel to the short edge and vertical elements to the long edge.</dd>

  <dt id="landscape">Landscape Orientation</dt>
  <dd>A landscape page's width is greater than or equal to its height. Horizontal
  elements are parallel to the long edge and vertical elements to the short edge.
  <span class="note">Note that CSS3 makes no distinction between landscape and
  reverse-landscape orientations. However, future versions of CSS may do so.
  UAs should consider, when formatting for duplexed printing, the binding edge,
  page progression, and ease of reading when choosing between landscape and
  reverse-landscape renderings.</span>
  </dd>

  <dt id="duplex-printing">Duplex Printing</dt>
  <dd>Duplex printing prints one page box per side of a page sheet and uses both
  sides of the page sheet. This module provides no ability to specify whether a
  document is duplex printed, but the concept of left and right pages is based on
  the assumption that the document is duplex printed, regardless of whether or
  not it actually is.</dd>

  <dt id="binding-edge">Binding Edge</dt>
  <dd>The binding edge is the edge of the page box that is toward the binding if the
  material is bound. The binding edge often has a larger margin than the opposite
  edge to provide for the space used by the binding. The binding edge can be any
  of the four edges. However, page sheets are customarily bound so that the
  binding edge of page boxes with portrait orientation is vertical. This module
  provides no method to specify the binding edge. In duplex printing, the binding
  edge is on opposite sides of the page box for the left and right pages.</dd>

  <dt id="facing-pages">Facing Pages</dt>
  <dd>Facing pages are two sequential pages such that when the document is duplex
  printed they are on separate sheets of paper. Typically, the earlier page will
  be the back side of one sheet and the later page will be the front side of
  another. They are usually laid out so that the binding edges of facing pages
  are vertical and adjacent when the pages are placed in their normal reading
  orientation.</dd>

  <dt><dfn id="left-page">Left Page</dfn></dt>
  <dd>A page that would be on the left if it is part of a pair of facing pages as
  typically laid out. Page layouts for documents using a left-to-right page
  progression have the earlier of the facing pages on the left. Rules specific to
  the left page can be specified using the '':left'' <i>page selector</i>.
  </dd>

  <dt><dfn id="right-page">Right Page</dfn></dt>
  <dd>A page that would be on the right if it is part of a pair of facing pages as
  typically laid out. Page layouts for documents using a right-to-left page
  progression have the earlier of the facing pages on the right. Rules specific
  to the right page can be specified using the '':right'' <i>page selector</i>.
  </dd>
</dl>


<h2 id="page-model">The Page Model</h2>

<p>In the paged media formatting model, the document is transferred into one
or more page boxes. The <dfn id="page-box">page box</dfn> is a specialized CSS
box that maps to a rectangular print media surface, such as a page of paper.
It is roughly analogous to the <a href="http://www.w3.org/TR/CSS21/visuren.html#viewport">viewport</a>.
<img src="PageBox.png" style="float: right;" alt="" height="266" width="267">

<p>As with other CSS <a href="http://www.w3.org/TR/CSS21/box.html">boxes</a>, a page box
consists of margin, border, padding, and content areas. The content and
margin areas of a page box have special functions:</p>

<p class="issue">
    In CSS 2.1, both the page box and page area are simple rectangles.
    Neither is a CSS box with margins, borders, and padding.
    This CSS box should be distinct from the page box and page area,
    which would be its margin area and content area, respectively.
    Naming ideas?

<ul>
  <li>The content area of a page box is called the <dfn id="page-area">page
  area</dfn>. The content of the document is flowed into one or more page boxes.
  The page area acts as a container for all the boxes generated by the root
  element and its descendants that are laid out within a given page box. The
  edges of the page area on the first page establish the rectangle that is the
  initial <a href="http://www.w3.org/TR/CSS21/visudet.html#containing-block-details">containing block</a>
  of the document.</li>
  <li>The margin area of a page box is divided into
  16 <dfn title="page-margin box">page-margin boxes</dfn>.
  Each page-margin box has its own margin, border, padding and content areas.
  Page-margin boxes are typically used to display running headers and footers.</li>
</ul>

<p>The properties of a <i>page box</i> are determined by properties
<a href="http://www.w3.org/TR/CSS21/syndata.html#declaration">declared</a> within the
<i>page context</i>, which is the
<a href="http://www.w3.org/TR/CSS21/syndata.html#x14">declaration block</a> of the
<code>@page</code> rule. Similarly the properties of a <i>page-margin box</i>
are determined by properties declared within its <i>margin context</i>.
Declarations in the page context can affect the page box and/or inherit
to the page-margin boxes, but they do not apply to or inherit into the
document's root element or other content.</p>

<p>The <i>containing block</i> of the page box is specified using the 'size'
property in the <i>page context</i>. The width and horizontal margins
of the page box are then calculated exactly as for a
<a href="http://www.w3.org/TR/CSS21/visudet.html#blockwidth">non-replaced
block element in normal flow</a>. [[!CSS21]] The height and vertical margins
of the page box are calculated analogously (instead of using the block height
formulas). In both cases if the values are over-constrained, instead of
ignoring any margins, the containing block is resized to coincide with the
margin edges of the page box.

<h3 id="painting">
Page Backgrounds and Painting Order</h3>

  <p>When drawing a page of content, the page layers are painted in the
  following painting order (bottommost first):

  <ol>
    <li>page background
    <li>document canvas
    <li>page borders
    <li>document contents
    <li>page-margin boxes
  </ol>

  <p>In the page model, the page background behaves similar to the root background:
  its <a spec=css-backgrounds>background painting area</a>
  is the entire page box, including its margins (regardless of 'background-clip').
  Page backgrounds are anchored within the page box's padding area by default
  (and honor 'background-origin' if the UA supports [[!CSS3BG]]).
  However if 'background-attachment' is ''fixed''
  then the image is positioned relative to the page box including its margins
  (i.e. the <a spec=css-backgrounds>background positioning area</a>,
  like the <a spec=css-backgrounds>background painting area</a>, is the page's margin box).

  <p>The document canvas background is drawn as the page box's background:
  by default its <a spec=css-backgrounds>background painting area</a> covers the page box's border box,
  and for UAs that support [[!CSS3BG]], follows the 'background-clip' value specified on the root element.
  It remains, however, positioned with respect to the root element
  or page area as usual.

  <p>
  With respect to the page-margin boxes,
  the document canvas, page borders, and all of the document contents
  are treated as a single element with a <code>z-index</code> value of '0'
  that establishes a
  <a href="http://www.w3.org/TR/CSS21/visuren.html#x43">stacking context</a>
  [[!CSS21]]:
  the page-margin boxes never interleave with parts of the document content
  or between the content and the canvas.
  They may only paint in front of the document content
  or behind the document canvas.
  The page background is always painted underneath everything else.

  <p>The 'z-index' property applies to page-margin boxes.
  Since the 'position' property does not apply to page-margin boxes,
  'z-index' always affects page-margin boxes as if they were positioned elements
  regardless of the 'position' property's value.
  Each page-margin boxes always establishes a stacking context.

  <p>The default painting order,
  or <a href="http://www.w3.org/TR/CSS21/zindex.html">CSS2.1 Appendix E</a> "tree order",
  of page-margin boxes with respect to each other is as follows:

  <ol>
    <li>''@top-left-corner''
    <li>''@top-left''
    <li>''@top-center''
    <li>''@top-right''
    <li>''@top-right-corner''

    <li>''@right-top''
    <li>''@right-middle''
    <li>''@right-bottom''

    <li>''@bottom-right-corner''
    <li>''@bottom-right''
    <li>''@bottom-center''
    <li>''@bottom-left''
    <li>''@bottom-left-corner''

    <li>''@left-bottom''
    <li>''@left-middle''
    <li>''@left-top''
  </ol>

  <p class=note>
    Start with ''@top-left-corner'', then go clockwise.
    This order is arbitrary but can be overridden with 'z-index'.
    It only has a visible effect when page-margin boxes overlap,
    which should not happen in most cases.

<h3 id="content-outside-box">Content outside the page box</h3>

<p>When formatting content in the page model, some content may end up outside the
page box. For example, an element whose 'white-space' property has the value
''pre'' can generate a box that is wider than the page box. As another example,
when boxes are positioned absolutely or relatively, they may end up in
"inconvenient" locations. For example, images may be placed on the edge of
the page box or 100,000 meters below the page box. </p>

<p>A specification for the exact formatting of such elements lies outside the
scope of this document. However, it is recommended that authors and user agents
observe the following general principles concerning content outside the page
box:</p>

<ul>
  <li><p>Content should be allowed slightly beyond the page box to allow pages
  to "bleed".
  <li><p>User agents <em class="RFC2119">SHOULD</em> avoid generating a large
  number of content-empty pages to honor the positioning of elements (e.g.,
  printing 100 blank pages is probably neither the author's nor the user's
  intent).
  A <dfn id="content-empty">Content-empty page</dfn> is a page box whose page
  area contains no printable content other than backgrounds and/or borders. A
  page box whose page area contains generated content, or content whose
  visibility is ''hidden'', or invisible content such as a zero-width space is
  not a content-empty page. On the other hand, a page containing only a
  background and/or borders and/or page-margin box content <em>is</em> a
  content-empty page.
  <p class="note">Note, however, that generating a small number of empty page
  boxes is sometimes necessary to honor the forced-break values for
  'page-break-before'/'break-before' and 'page-break-after'/'break-after'.
  [[!CSS21]] [[!CSS3-BREAK]]</li>

  <li><p>Authors <em class="RFC2119">SHOULD NOT</em> position elements in
  inconvenient locations just to avoid rendering them. Instead:
  <ul>
    <li>To suppress box generation entirely, set the 'display' property to ''none''.</li>
    <li>To make a box invisible, set the <span class="property">'visibility'</span>
    property.</li>
    </ul></li>
    <li><p>This specification does not define how boxes positioned outside the page
    box are handled. Possibilities include discarding them or creating page boxes
    for them at the end of the document.</li>
</ul>

<h3 id="progression">Page Progression</h3>

<p>CSS distinguishes between left pages and right pages on all documents,
whether they are printed duplex or not. Each left page is followed by a
right page and vice versa. Left and right pages can be styled differently
with the <a href="#left-right-first"><code>:left</code> and <code>:right</code>
pseudo-classes</a>.

<p>Whether the first page of a document is a left page or a right page
depends on the page progression of the document. The <dfn>page progression</dfn>
is the direction in which the printed pages of a document would be sequenced
when laid out side-to-side. For example, English and horizontally-set Japanese
typically progress from left to right, whereas Arabic and vertically-set
Japanese pages typically progress from right to left. In documents with
a left-to-right page progression the first page of the document is a right
page, and vice versa.</p>

<p>The page progression direction is determined as follows:</p>

<ul>
  <li>If text is laid out in horizontal lines, the page progression is the
  same as the inline progression.</li>
  <li>If text is laid out in vertical lines, the page progression is the
  same as the block progression.</li>
</ul>

<p>If the UA supports the 'direction' and 'writing-mode' properties
from the CSS 3 Writing Modes Module [[CSS3-WRITING-MODES]], it must
<a href="http://www.w3.org/TR/css3-writing-modes/#page-direction">determine</a>
whether the first page is a left or right page from the values of those
properties on the root element.</p>

<p>
  To explicitly force a document to begin printing on a left or right page,
  authors can specify a <a href="http://www.w3.org/TR/css3-break/#break-before">'break-before'</a> value
  that that propagates a page break to the root. [[!CSS3-BREAK]]
  The UA must suppress the first (empty) page(s) in this case
  (and the <code>:first</code> pseudo-class matches the first printed page).

<div class="example">
<pre>
html { break-before: always }
</pre>

<p>
  For an HTML document with a left-to-right page progression,
  the above style rule will cause the first page of the document
  to print on a ':left' page
</p>

<pre>
html { break-before: left }
</pre>

<p>
  For an HTML document,
  the above style rule will cause the first page of the document
  to print on a ':left' page,
  regardless of the page progression.
</p>
</div>

<h2 id="page-selector-and-context">
Page Selectors and the Page Context</h2>

<h3 id="at-page-rule"><span id="page-box-page-rule"></spans>
The @page Rule</h3>

  <p>Authors can specify various aspects of a page box,
  such as its dimensions, orientation, and margins,
  within an ''@page'' rule.
  ''@page'' rules are allowed
  wherever <a href="http://www.w3.org/TR/CSS21/syndata.html#rule-sets">rule-sets</a> are allowed.
  An ''@page'' rule consists of the keyword ''@page'',
  an <em class="RFC2119">OPTIONAL</em> comma-separated list of
  <a href="#page-selectors">page selectors</a>
  and a block of declarations
  (said to be in the <dfn id="page-context">page context</dfn>).
  An ''@page'' rule can also contain other at-rules,
  interleaved between declarations.
  The current level of this specification
  only allows <a href="#margin-at-rules">margin at-rules</a> inside ''@page''.

  <p>''@page'' rules without a selector list apply to every page.
  Other ''@page'' rules apply to pages that <i>match</i>
  at least one of their selectors.
  Properties declared within the page context apply to the page box.


<p>If an error is encountered during the processing of a declaration block within
a page or a margin context, the <a href="http://www.w3.org/TR/CSS21/syndata.html#parsing-errors">Rules for handling parsing errors</a>
apply; that is, valid declarations within the block are applied.</p>


<h3 id="page-selectors">Page selectors</h3>

  <p>A <dfn id="page-selector">page selector</dfn> is made of
  either a <i>page type selector</i>
  or a <i>page pseudo-class</i>,
  followed by zero or more additional <i>page pseudo-classes</i>.
  No whitespace is allowed between components of a selector.
  The <i title="page_selector">page selector grammar</i>
  and examples can be found below.

  <p>A <i>page selector</i> is said to <dfn>match</dfn> a given page if and only if
  all of its components match the page.

  <p>A <dfn>page type selector</dfn> is
  a case-sensitive <a href="http://www.w3.org/TR/CSS21/syndata.html#value-def-identifier">CSS identifier</a> [[!CSS21]].
  It <i>matches</i> pages of the <a href="#using-named-pages">named page type</a>
  generated by the 'page' property.
  <span id="page-selector-syntax-restrict">
    A page type name of ''auto''
    (<a href="http://www.w3.org/TR/CSS21/syndata.html#characters">ASCII case-insensitive</a>)
    does not make the rule invalid,
    but <em class="RFC2119">MUST</em> never match.
  </span>

  <p>A <dfn>page pseudo-class</dfn> is <a href="http://www.w3.org/TR/CSS21/syndata.html#characters">ASCII case-insensitive</a>
  and has the same syntax as <a href="http://www.w3.org/TR/selectors/#pseudo-classes">pseudo-classes</a> in regular Selectors. [[!SELECT]]
  The various <i>page pseudo-classes</i> are defined below.

<h4 id="spread-pseudos"><span id="left-right-first"></span>
Spread pseudo-classes: '':left'', '':right''</h4>

  <p>When printing double-sided documents,
  left and right pages are often formatted differently.
  This can be expressed by using the '':left'' and '':right'' page pseudo-classes.

  <p dfn-type="value" dfn-for="@page">All pages are automatically classified by user agents
  as either left pages or right pages,
  based on <a href="#progression">page progression</a>.
  The <dfn>:left</dfn> and <dfn>:right</dfn> pseudo-classes
  only <i>match</i> <i title="left page">left</i> or <i title="right page">right pages</i>,
  respectively.

<div class="example">
The following example creates left and right binding edges using these pseudo-classes:
<pre>
@page :left {
margin-left: 3cm;
margin-right: 4cm;
}

@page :right {
margin-left: 4cm;
margin-right: 3cm;
}
</pre>
</div>

<p>If different declarations have been given for left and right pages, the user
agent <em class="RFC2119">MUST</em> honor these declarations even if the user
agent does not transfer the page boxes to left and right sheets (i.e., a
printer that only prints on one side of the medium must nevertheless produce
correctly formatted output).</p>

<div class="note">
<p>
  <em><strong>Note.</strong>
  Adding declarations to the '':left'' or '':right'' pseudo-class
  does not necessarily influence whether the document
  comes out of the printer double- or single-sided
  (which is outside the scope of this specification).</em>
</p>
</div>

<h4 id="first-pseudo">
First-page pseudo-class: '':first''</h4>

  <p>The <dfn dfn-type="value" dfn-for="@page">:first</dfn> pseudo-class <i title="match">matches</i>
  the first printed page of a document.

<div class="example">
<pre>
@page { margin: 2cm } /* All margins set to 2cm */

@page :first {
margin-top: 10cm /* Top margin on first page 10cm */
}
</pre>
</div>

<h4 id="blank-pseudo">
Blank-page pseudo-class: '':blank''</h4>

  <p>The <dfn dfn-type="value" dfn-for="@page">:blank</dfn> pseudo-class <i title="match">matches</i>
  <i title="content-empty page">content-empty pages</i>
  that appear as a result of
  <a href="http://www.w3.org/TR/css3-break/#forced-breaks">forced page breaks</a>.

  <div class="note">
    <p>Only the ''left'', ''right'', ''recto'' and ''verso'' values
    of the 'break-before' and 'break-after' properties
    can generate pages that match '':blank''.
  </div>

<div class="example">
<p>In this example, forced page break may occur before <code>h1</code> elements.
<pre>
h1 { break-before: left }

@page :blank {
  @top-center { content: "This page is intentionally left blank" }
}
</pre>
</div>

<p>
  A page matched by '':blank'' can also be matched
  by other page pseudo-classes.

<div class="example">

<p>If headers have been specified on all right pages, a blank right
page will be matched by both <code>:blank</code>
and <code>:right</code>. Therefore, margin boxes set on right pages
will have to be removed unless they are wanted on blank pages. Here is
an example where the top center header is removed from blank pages,
while the page number remains:

<pre>
h1 { break-before: left }

@page :blank {
  @top-center { content: none }
}

@page :right {
  @top-center { content: "Preliminary edition" }
  @bottom-center { content: counter(page) }
}
</pre>

<p>Due to the higher <i>specificity</i> of <code>:blank</code>
over <code>:right</code>, the top center header is removed even
if <code>content: none</code> comes before <code>content: "Preliminary
edition"</code>.

</div>

<div class="note">
<p><em><strong>Note.</strong> Future versions of CSS may include other page
pseudo-classes.</em></p>
</div>

<h3 id="syntax-page-selector">@page rule grammar</h3>

<p>The syntax for the @page rule is a specialization of the generic at-rule
defined by CSS 2.1. This grammar extends the at-rule syntax to allow @page rules
nested inside @media rules. User agents <em class="RFC2119">MUST</em> adhere
to the following grammar:</p>

<p>See [[!CSS21]], Section 4.1.1 and Appendix G for the expansion of missing
productions:</p>
<p id="specializatons-of-ATKEYWORD">
All new lexical tokens are specializations of the ATKEYWORD lexical token:</p>
<pre class="lexical">
PAGE_SYM              ::= "@page"
TOPLEFTCORNER_SYM     ::= "@top-left-corner"
TOPLEFT_SYM           ::= "@top-left"
TOPCENTER_SYM         ::= "@top-center"
TOPRIGHT_SYM          ::= "@top-right"
TOPRIGHTCORNER_SYM    ::= "@top-right-corner"
BOTTOMLEFTCORNER_SYM  ::= "@bottom-left-corner"
BOTTOMLEFT_SYM        ::= "@bottom-left"
BOTTOMCENTER_SYM      ::= "@bottom-center"
BOTTOMRIGHT_SYM       ::= "@bottom-right"
BOTTOMRIGHTCORNER_SYM ::= "@bottom-right-corner"
LEFTTOP_SYM           ::= "@left-top"
LEFTMIDDLE_SYM        ::= "@left-middle"
LEFTBOTTOM_SYM        ::= "@left-bottom"
RIGHTTOP_SYM          ::= "@right-top"
RIGHTMIDDLE_SYM       ::= "@right-middle"
RIGHTBOTTOM_SYM       ::= "@right-bottom"

<dfn>media</dfn> :
     MEDIA_SYM S* medium [ COMMA S* medium ]* LBRACE S* [ <i>page_rule</i> | ruleset ]* '}' S*
     ;

<dfn id="syntax-prod-page">page_rule</dfn> :
     PAGE_SYM S* <i>page_selector_list</i> '{' S* <i>page_body</i> '}' S*
     ;

<dfn>page_selector_list</dfn> :
     [ <i>page_selector</i> S* [ ',' <i>page_selector</i> S* ]* ]?
     ;

<dfn>page_selector</dfn> :
     <i>pseudo_page</i>+ | IDENT <i>pseudo_page</i>*
     ;

<dfn id="syntax-prod-pseudo-page">pseudo_page</dfn> :
     ':' [ "left" | "right" | "first" | "blank" ]
     ;

<dfn>page_body</dfn> :  /* Can be empty */
     declaration? [ ';' S* <i>page_body</i> ]? |
     <i>page_margin_box</i> <i>page_body</i>
     ;

<dfn id="syntax-prod-margin">page_margin_box</dfn> :
     <i>margin_sym</i> S* '{' S* declaration? [ ';' S* declaration? ]* '}' S*
     ;

<dfn id="syntax-prod-margin-sym">margin_sym</dfn> :
     TOPLEFTCORNER_SYM |
     TOPLEFT_SYM |
     TOPCENTER_SYM |
     TOPRIGHT_SYM |
     TOPRIGHTCORNER_SYM |
     BOTTOMLEFTCORNER_SYM |
     BOTTOMLEFT_SYM |
     BOTTOMCENTER_SYM |
     BOTTOMRIGHT_SYM |
     BOTTOMRIGHTCORNER_SYM |
     LEFTTOP_SYM |
     LEFTMIDDLE_SYM |
     LEFTBOTTOM_SYM |
     RIGHTTOP_SYM |
     RIGHTMIDDLE_SYM |
     RIGHTBOTTOM_SYM
     ;
</pre>

<div class="example">
<p>The following are examples of page selectors (declaration block intentionally
left blank)</p>
<pre>
@page { ... }
@page :left { ... }
@page :right { ... }
@page LandscapeTable { ... }
@page CompanyLetterHead:first { ... } /*  identifier and pseudo page. */
@page:first { ... }
@page toc, index { ... }
@page :blank:first { ... }
</pre>

<p>The following are examples of page-margin boxes
where the declaration blocks are intentionally left blank.</p>
<pre>
@page {
 @top-left { ... /* document name */ }
 @bottom-center { ... /* page number */}
}
@page :left { @left-middle { ... /* page number in left margin */ }}
@page :right{ @right-middle { ... /* page number in right margins of right pages */}}

@page :left { @bottom-left-corner { ... /* left page numbers */ }}
@page :right { @bottom-right-corner { ... /* right page numbers */ }}
@page :first { @bottom-left-corner { ... /* empty footer on 1st page */ }
             @bottom-right-corner { ... /* empty footer */ } }
</pre>
</div>

<h3 id="cascading-and-page-context">Cascading in the page context</h3>

<p>Declarations in page and margin contexts <a href="http://www.w3.org/TR/CSS21/cascade.html">cascade</a> just like declarations in style rule for elements.</p>

<p>The <dfn>specificity</dfn> of page a selector is computed in a manner
analogous to the computations defined in
the <a href="http://www.w3.org/TR/CSS21/selector.html">Selectors</a> module:

<ul>
  <li>Count the number of page type names (= <var>f</var>)
    <p class="note">
      Given the syntax of page seletors, <var>f</var> can only ever be 0 or 1.
  <li>Count the number of ':first' or ':blank' pseudo-classes (= <var>g</var>)
  <li>Count the number of ':left' or ':right' pseudo-classes (= <var>h</var>)
</ul>

<p class="note">
  Note: Repeated occurrences of the same pseudo-classes are allowed
  and do increase specificity.

<p>
  Due to storage limitations,
  implementations may have limitations on
  the size of <var>f</var>, <var>g</var>, or <var>h</var>.
  If so, values higher than the limit must be clamped to that limit,
  and not overflow.

<p>
  Specificities are compared by comparing the three components in order
  (<var>f</var>, <var>g</var>, <var>h</var>):
  the specificity with a larger <var>f</var> value is more specific;
  if the two <var>f</var> values are tied,
  then the two <var>g</var> values are compared, etc.
  If all the values are tied, the two specificities are equal.

<div class="example">

<p>Some page specificity calculation examples follow:</p>
<pre>
@page { } /* specificity = (0,0,0) */
@page :left { } /* specificity = (0,0,1) */
@page :first { } /* specificity = (0,1,0) */
@page :blank:left { } /* specificity = (0,1,1) */
@page artsy { } /* specificity = (1,0,0) */
@page artsy:left { } /* specificity = (1,0,1) */
@page artsy:first { } /* specificity = (1,1,0) */
</pre>
</div>

<div class="example">

<p>Consider the following usage example:</p>
<pre>
@page :left {
  margin-left: 4cm;
}

@page {
  margin-left: 3cm;
}
</pre>

<p>Due to the higher specificity of the pseudo-class selector,
the left margin on left pages will be 4cm and all other pages
(the right-facing pages) will have a left margin of 3cm.
</div>

<div class="example">
<p>In this example, the higher specificity of the green rules wins over the red
rule.
Therefore the first page will have blue text in the top-left page-margin box
and green text in the top-right page-margin box,
while subsequent pages will have red text in the page-margin boxes.</p>
<pre>
@page :first {
  color: green;

  @top-left {
    content: "foo";
    color: blue;
  }
  @top-right {
    content: "bar";
  }
}

@page { color: red;
  @top-center {
    content: "Page " counter(page);
  }
}
</pre>
</div>

<div class="example">

<p>Page contexts cascade, so the following stylesheet would style pages with 25
millimeter margins and 14 point type in the page-margin boxes:</p>
<pre>
@page { margin: 25mm;}
@page { font-size: 14pt;}
</pre>
</div>

<h2 id="margin-boxes">Page-Margin Boxes</h2>

  <p>Page-margin boxes are boxes within the page margin that,
  like pseudo-elements, can contain generated content.

  <p>Page-margin boxes can be used to create page headers and footers,
  which are portions of the page set aside for supplementary information
  such as the page number or document title.

  <div class="example">
    <p>Typically, a <dfn>page header</dfn> is located at the top of the page
    in documents with a predominately horizontal writing direction
    and on the side opposite the <a href="#binding-edge">binding edge</a>
    for documents with a predominately vertical writing direction.
    One possible design of page headers for horizontally written documents uses the
    ''@top-left-corner'', ''@top-left'', ''@top-center'', ''@top-right'' and ''@top-right-corner''
    page-margin boxes.
    Another design, for vertically written documents, could use the
    ''@right-top'', ''@right-middle'', and ''@right-bottom'' page-margin boxes
    for <a href="#right-page">right facing pages</a> and
    ''@left-top'', ''@left-middle'', and ''@left-bottom''
    for <a href="#left-page">left facing pages</a>.

    <p>The <dfn>page footer</dfn> is typically at
    the opposite end of the page from the page header.
    For example, the design of a horizontally written document with a page header
    at the top of the page could use the
    ''@bottom-left-corner'', ''@bottom-left'', ''@bottom-center'', ''@bottom-right'' and ''@bottom-right-corner''
    page-margin boxes as the page footer.
    The design of a vertically written document could use
    the page-margin boxes of the binding edge of the page for the page footer.
  </div>

  <p>Page-margin boxes are positioned with respect to the page area
  and are independent of page orientation,
  for example the top page-margin boxes are above the page area
  in both portrait and landscape orientation.
  The various page-margin boxes are defined
  and illustrated in the diagram below:

  <table id="margin-box-def" class="data" summary="defintion of each of the page-margin boxes">
    <caption>Table 1 Page-Margin Box Definitions</caption>
    <thead>
      <tr>
        <th>Box</th>
        <th>Description</th>
        <th>Placement</th>
      </tr>
    </thead>
    <tbody>
      <tr id="top-margin-boxes-def">
        <th id="top-left-corner-box-def">top-left-corner</th>
        <td>a fixed-size box defined by the intersection of the top and left margins of the
        page box</td>
        <td><img src="TopLeftCornerBox.png" alt="the top left corner box with margin, border, and padding, nested within intersection of the page's top and left margins"
        height="47" width="181"></td>
      </tr>
      <tr id="top-left-box-def">
        <th>top-left</th>
        <td>a variable-width box filling the top page margin between the top-left-corner
        and top-center page-margin boxes</td>
        <td><img src="TopLeftMarginBox.png" alt="the top left box with margin, border, and padding, nested in the page's top margin next to the top left corner box"
        height="47" width="181"></td>
      </tr>
      <tr id="top-center-box-def">
        <th>top-center</th>
        <td>a variable-width box centered horizontally between the page's left and right
        border edges and filling the page top margin between the top-left and top-right
        page-margin boxes</td>
        <td><img src="TopCenterMarginBox.png" alt="the top center box with margin, border, and padding, centered within the page's top margin"
        height="47" width="181"></td>
      </tr>
      <tr id="top-right-box-def">
        <th>top-right</th>
        <td>a variable-width box filling the top page margin between the top-center and
        top-right-corner page-margin boxes</td>
        <td><img src="TopRightMarginBox.png" alt="the top right box with margin, border, and padding, nested within the page's top margin"
        height="47" width="181"></td>
      </tr>
      <tr>
        <th id="top-right-corner-box-def">top-right-corner</th>
        <td>a fixed-size box defined by the intersection of the top and right margins of
        the page box</td>
        <td><img src="TopRightCornerMarginBox.png" alt="the top right corner box with margin, border, and padding, nested within the intersection of the page's top and right margin"
        height="47" width="181"></td>
      </tr>
      <tr id="left-margin-boxes-def">
        <th id="left-top-box-def">left-top</th>
        <td>a variable-height box filling the left page margin between the top-left-corner
        and left-middle page-margin boxes</td>
        <td rowspan="3"><img src="LeftMarginBoxes.png" alt="left-top, left-middle, and left-bottom page-margin boxes in the page box's left margin"
        height="226" width="181"></td>
      </tr>
      <tr id="left-middle-box-def">
        <th>left-middle</th>
        <td>a variable-height box centered vertically between the page's top and bottom
        border edges and filling the left page margin between the left-top and
        left-bottom page-margin boxes</td>
      </tr>
      <tr id="left-bottom-box-def">
        <th>left-bottom</th>
        <td>a variable-height box filling the left page margin between the left-middle and
        bottom-left-corner page-margin boxes</td>
      </tr>
      <tr id="right-margin-boxes-def">
        <th id="right-top-box-def">right-top</th>
        <td>a variable-height box filling the right page margin between the
        top-right-corner and right-middle page-margin boxes</td>
        <td rowspan="3"><img src="RightMarginBoxes.png" alt="right-top, right-middle, and right-bottom page-margin boxes in the page box's right margin"
        height="226" width="181"></td>
      </tr>
      <tr id="right-middle-box-def">
        <th>right-middle</th>
        <td>a variable-height box centered vertically between the page's top and bottom
        border edges and filling the right page margin between the right-top and
        right-bottom page-margin boxes</td>
      </tr>
      <tr id="right-bottom-box-def">
        <th>right-bottom</th>
        <td>a variable-height box filling the right page margin between the right-middle
        and bottom-right-corner page-margin boxes</td>
      </tr>
      <tr id="bottom-margin-boxes-def">
        <th id="bottom-left-corner-box-def">bottom-left-corner</th>
        <td>a fixed-size box defined by the intersection of the bottom and left margins of
        the page box</td>
        <td><img src="BottomLeftCornerBox.png" alt="bottom left corner box with margin, border, and padding, nested within the page margin at the intersection of the left and bottom page margins"
        height="48" width="181"></td>
      </tr>
      <tr id="bottom-left-box-def">
        <th>bottom-left</th>
        <td>a variable-width box filling the bottom page margin between the
        bottom-left-corner and bottom-center page-margin boxes</td>
        <td><img src="BottomLeftMarginBox.png" alt="bottom left page-margin box with margin, border, and padding, nested within the page's bottom margin next to the bottom-left-corner box"
        height="48" width="181"></td>
      </tr>
      <tr id="bottom-center-box-def">
        <th>bottom-center</th>
        <td>a variable-width box centered horizontally between the page's left and right
        border edges and filling the bottom page margin between the bottom-left and
        bottom-right page-margin boxes</td>
        <td style="vertical-align: middle;"><img src="BottomCenterMarginBox.png" alt="bottom center box with margin, border, and padding, nested within the page's bottom margin and centered on the page"
        height="48" width="181"></td>
      </tr>
      <tr id="bottom-right-box-def">
        <th>bottom-right</th>
        <td>a variable-width box filling the bottom page margin between the bottom-center
        and bottom-right-corner page-margin boxes</td>
        <td><img src="BottomRightMarginBox.png" alt="bottom right page-margin box with margin, border, and padding, nested within the page's bottom margin and next to the bottom-right-corner box"
        height="48" width="181"></td>
      </tr>
      <tr id="bottom-right-corner-box-def">
        <th>bottom-right-corner</th>
        <td>a fixed-size box defined by the intersection of the bottom and right margins of
        the page box</td>
        <td><img src="BottomRightCornerBox.png" alt="bottom right corner box with margin, border, and padding, nested within the page margin at the intersection of the right and bottom page margins"
        height="48" width="181"></td>
      </tr>
    </tbody>
  </table>

<h3 id="margin-at-rules">At-rules for page-margin boxes</h3>

<p>Page-margin boxes are created by
<a href="#margin-at-rules">margin at-rules</a>
inside the <a href="#page-context">page context</a>.
Authors should put these rules after any declarations in the page context
as legacy clients may not handle declarations
after margin at-rules correctly.
</p>

<p>A <dfn id="margin-at-rule">margin at-rule</dfn> consists of an
<a href="#specializatons-of-ATKEYWORD">ATKEYWORD</a>
that identifies the page-margin box
(e.g. ''@top-left'') and a block of declarations (said
to be in the <dfn id="margin-context">margin context</dfn>).</p>

<div class="example">

<p>The following style sheet establishes a page header containing the title
("Hamlet") on the left side and the page number, preceded by "Page ", on the
right side:</p>
<pre>
@page {
  size: 8.5in 11in;
  margin: 10%;

  @top-left {
    content: "Hamlet";
  }
  @top-right {
    content: "Page " counter(page);
  }
}
</pre>
</div>


<h3 id="populating-margin-boxes">Populating page-margin boxes</h3>

<p>As with the '':before'' and '':after'' pseudo-elements,
a specified 'content: normal' on a page-margin box computes to ''none''.
A page-margin box is <dfn>generated</dfn>
if and only if the computed value of its 'content' property is not ''none''.
Otherwise, no box is generated, as for elements with ''display: none''.

<p class=note>
  The 'display' property does not apply to page-margin boxes.

<div class="example">
<p>The following style sheet creates a green box in each corner of the page
except the bottom-left corner.</p>
<pre>
  @page {
    @top-left-corner { content: " "; border: solid green; }
    @top-right-corner { content: url(foo.png); border: solid green; }
    @bottom-right-corner { content: counter(page); border: solid green; }
    @bottom-left-corner { content: normal; border: solid green; }
  }
</pre>
</div>

<h3 id="margin-dimension">Computing Page-margin Box Dimensions</h3>

<p>The width and height of each page-margin box is determined by the rules
below. These rules define the equivalent of CSS2.1 Sections 10.3 and
10.6 for page-margin boxes.</p>

<p>The rules for applying 'min-height', 'max-height', 'min-width', and
'max-width' [[!CSS21]] do apply to page-margin boxes and may imply
a recalculation of the width, height, and/or margins
if the dimensions resulting from the specified 'width' or 'height'
violate their constraints.
If the UA does not support the 'min-height' or 'min-width' properties
then it must behave as if 'min-height' and 'min-width' were always zero.

<h4 id="margin-box-terms"><span id="max-margin-dimension"></span>Page-Margin Box Layout Terminology</h4>

  <p>In addition to the box model definitions in CSS2.1 [[!CSS21]],
  and the sizing terms in CSS Intrinsic Sizing [[!CSS3-SIZING]],
  the following terms are defined for use
  in the subsequent page-margin box calculations:

  <dl>

    <dt><dfn>available width</dfn></dt>
    <dd>The sum of the page’s
      left border width, left padding, <a href="#page-box">page area</a> width,
      right padding, and right border width.
      In other words, it is the distance between
      the <a href="#page-box">page box</a>’s left right border edges.
      This quantity is used  when calculating dimensions
      of the top and bottom page-margin boxes.

    <dt><dfn>available height</dfn></dt>
    <dd>The sum of the page’s
      top border width, top padding, <a href="#page-box">page area</a> height,
      bottom padding, and bottom border width.
      In other words, it is the distance between
      the <a href="#page-box">page box</a>’s top bottom border edges.
      This quantity is used when calculating dimensions
      of the left and right page-margin boxes.

    <dt><dfn>outer width</dfn></dt>
    <dd>The width of the
      <a href="http://www.w3.org/TR/CSS21/box.html#outer-edge">outer edge</a>,
      as defined in [[!CSS21]].

    <dt><dfn>min-content width</dfn></dt>
    <dd>Whichever of <a spec=css-sizing>min-content measure</a>
    or <a spec=css-sizing>min-content extent</a> is the physical width.

    <dt><dfn>max-content width</dfn></dt>
    <dd>Whichever of <a spec=css-sizing>max-content measure</a>
    or <a spec=css-sizing>max-content extent</a> is the physical width.

    <dt><dfn>outer min width</dfn></dt>
    <dd>Like the <i>outer width</i>,
    except the <a>min-content width</a> is used when the computed 'width' is ''auto''.

    <dt><dfn>outer max width</dfn></dt>
    <dd>Like the <i>outer width</i>,
    except the <a>max-content width</a> is used when the computed 'width' is ''auto''.
  </dl>

  <p>The <dfn>containing block</dfn> for a page-margin box depends on its location:

  <p>For a corner page-margin box,
  it is the rectangle defined by the intersection of the two page margins meeting at that corner.

  <p>For all other page-margin boxes,
  the <a>containing block</a> is the rectangle
  formed by the encapsulating page margin minus the containing blocks of the
  adjacent corners' page-margin boxes.
  This means that the size of this containing block is given
  in one dimension by the used page margin and in the other dimension
  by the <i>available width</i>
  (for top and bottom page-margin boxes) or
  <i>available height</i>
  (for left and right page-margin boxes).</p>

<h4 id="variable-sizing">
Page-Margin Box Variable Dimension Computation Rules</h4>

<p>The following rules apply to ''@top-left'', ''@top-center'' and ''@top-right''
page-margin boxes,
which are referred to as A, B, and C, respectively, in this section.</p>

<h5 id="variable-auto-margins">Margins</h5>

<p>If the 'margin-left' or 'margin-right' property of any of the three boxes
computes to ''auto'', the used value is zero.</p>

<h5 id="variable-auto-sizing">Resolving ''auto'' widths</h5>

<p>The following algorithm determines the used width of each box.
For this purpose, boxes that are not <i>generated</i>
are assumed to have a 'width' and an <i>outer width</i> of zero.
</p>

<p class="note">
Note: The high-level goals are (in order of priority) to center the middle
box (B) if it is generated, to minimize overflow and overlap, and to
distribute space proportionally to the amount of content.</p>

  <p>If the middle box (B) is not <i>generated</i>,
  distribute the <i>available width</i> to A and C as follows:

  <ul>
    <li>
      If only one box has 'width: auto',
      its used width is resolved so that
      the sum of the <i>outer width</i>s equals <i>available width</i>.
    </li>

    <li id="flex-fit">
      If A and C both have 'width: auto', distribute the space to each box as follows:
      <ol>
        <li>If the sum of the outer <i>max-content widths</i> is less than the <i>available width</i>,
            call that difference the <dfn>flex space</dfn>.
            Calculate each box's <dfn>flex factor</dfn> as proportional to
            its outer <i>max-content width</i>,
            and set its used outer width to:
            <p><code><i>max-content width</i> + <i>flex space</i> × <i>flex factor</i> ÷ ∑<i>flex factors</i></code></p>
        <li>Otherwise if the sum of the outer <i>min-content widths</i> is less than the <i>available width</i>,
            call that difference the <i>flex space</i>
            calculate each box's <i>flex factor</i> as proportional to
            its <i>max-content width</i> minus <i>min-content width</i>,
            and set its used outer width to:
            <p><code><i>min-content width</i> + <i>flex space</i> × <i>flex factor</i> ÷ ∑<i>flex factors</i></code></p>
        <li>Otherwise,
            calculate its outer size as in the previous case,
            but set each box's <i>flex factor</i> as proportional to
            its outer <i>min-content width</i>.
      </ol>
      In each case, both <i>flex factors</i> are assumed to be ''1'' if their sum is equal to zero.
    </li>
  </ul>

  <p>If the middle box (B) is <i>generated</i>,
  determine the ''auto'' widths of A, B, and C as follows:

  <ol>
    <li>
      First, resolve any ''auto'' width of the middle box (B):
      Assume there are two boxes, B and AC,
      where each of AC's dimensions is double the maximum of A and C.
      (This preserves B's centering.)
      Distribute the space to these two boxes (B and the imaginary AC)
      as described for A and C <a href="#flex-fit">above</a>.
    <li>
      Then, resolve any ''auto'' widths of the side boxes (A and C)
      by setting that box's outer width to
      <p><code>(<i>available width</i> &minus; used <i>outer width</i>s of B) ÷ 2</code></p>
    </li>
  </ol>

<h5 id="variable-minmax">Handling 'min-width' and 'max-width'</h5>

<p>
  The 'min-width' and 'max-width' properties [[CSS21]] apply to page-margin
  boxes in the variable dimension like on normal elements, except that the
  three boxes on the same side are considered together.
</p>

<p>
  More precisely:
</p>

<ol>
  <li>
    The tentative used widths are calculated
    (without 'min-width' and 'max-width') following the rules under
    <a href="#variable-auto-sizing">Resolving ''auto'' widths</a>
    above.
  </li>
  <li>
    If the tentative used width of any of the three boxes
    is greater than 'max-width', the rules above are applied again,
    but this time using the computed value of 'max-width'
    as the computed value for 'width'.
  </li>
  <li>
    If the resulting width of any of the three boxes
    is smaller than 'min-width', the rules above are applied again,
    but this time using the value of 'min-width'
    as the computed value for 'width'.
  </li>
</ol>

<h5 id="variable-position">Positioning</h5>

<p>
  Once the dimensions of the boxes are determined,
  they are positioned as follows:
</p>

<ul>
  <li>The left outer edge of A is flush with the left edge of the
      containing block</li>
  <li>The outer area of B is centered in the containing block.</li>
  <li>The right outer edge of C is flush with the right edge of the
      containing block.</li>
</ul>

<h5 id="variable-mapping">Boxes on other sides</h5>

<p>The used values for ''@bottom-left'', ''@bottom-center'' and ''@bottom-right''
page-margin boxes are established by the same rules as
for ''@top-left'', ''@top-center'', and ''@top-right'', respectively.</p>

<p>The used values for ''@left-top'', ''@left-middle'' and ''@left-bottom'' boxes are
established by the same rules, with "width" replaced by "height", "left" by
"top", "right" by "bottom" and "center" by "middle".</p>

<p>The used values for ''@right-top'', ''@right-middle'' and ''@right-bottom''
page-margin boxes
are established by the same rules as for ''@left-top'', ''@left-middle'' and
''@left-bottom'', respectively.</p>

<h4 id="fixed-sizing">Page-Margin Box Fixed Dimension Computation Rules</h4>

<p>The rules below are used to calculate the used values of each
''@top-left-corner'', ''@top-left'', ''@top-center'', ''@top-right'', and
''@top-right-corner'' page-margin box's 'height', 'margin-top', and 'margin-bottom'
properties:</p>

<ol>
  <li>The following constraint must hold among the used values of the margin
  box's properties:
  <p>'margin-top' + 'border-top-width' + 'padding-top' + 'height' +
  'padding-bottom' + 'border-bottom-width' + 'margin-bottom' = top page margin

  <li>If 'border-top-width' + 'padding-top' + 'height' (if it is not ''auto'')
  + 'padding-bottom' + 'border-bottom-width', plus 'margin-top' and/or
  'margin-bottom' if not ''auto'', is larger than the height of the top page
  margin, then any ''auto'' values for 'margin-top' or 'margin-bottom' are, for
  the following rules, treated as zero.

  <li>If at this point all of 'height', 'margin-top', and 'margin-bottom'
  have a computed value other than ''auto'', the values are said to be
  "over-constrained". In this case, the specified value of 'margin-top' is
  treated as ''auto''.

  <li>If there is now exactly one value specified as ''auto'', its used value
  follows from the equality.

  <li>If 'height' is set to ''auto'', any other ''auto'' values become '0' and
  'height' follows from the resulting equality

  <li>If both 'margin-top' and 'margin-bottom' are ''auto'',
  their used values are equal.
  This vertically centers the page-margin box content
  within the top page margin.
</ol>

<p>The same rules apply to the bottom page-margin boxes (bottom-left-corner,
bottom-left, bottom-center, bottom-right, and bottom-right-corner), except that
in the overconstrained case, the 'margin-bottom' is ignored rather than the
'margin-top'.</p>

<p>Analogous rules govern the properties for the left and right
page-margin boxes with respect to 'width'
(top-left-corner, left-top, left-middle, left-bottom, and
bottom-left-corner; top-right-corner, right-top, right-middle, right-bottom,
bottom-right-corner), with "top" replaced by "left", "bottom" replaced by
"right", and "height" replaced by "width".
In the overconstrained case for left (right) page-margin boxes,
the specified value of 'margin-left' ('margin-right') is ignored.</p>

<h3 id="margin-box-ex">Page-margin box examples</h3>

<p>The following is a collection of examples of page-margin box usage.</p>

<div class="example">

<p>Here is an example of a page with only a top-left header:</p>
<pre>
@page {
@top-left { content: "Header in Left Cell (top-left)" }
}
</pre>

<p>Because there are no contents defined for the top-center or the top-right
page-margin boxes, the extent of the top-left page-margin box
is allowed to cross the center of the page box.</p>

<p><img alt="Header Example 1" src="header-ex-1.png" height="177" width="737"></p>
</div>

<div class="example">

<p>The following is an example of a page with a centered header:</p>
<pre>
@page {
@top-center { content: "Header in Center Cell (top-center)" }
}
</pre>

<p><img alt="Header Example 2" src="header-ex-2.png" height="177" width="737"></p>
</div>

<div class="example">

<p>The following is an example of a page with a single header in the top-right
page-margin box:</p>
<pre>
@page {
@top-right { content: "Header in Right Cell (top-right)" }
}
</pre>

<p>Because the content of the center cell is empty, the extent of the top-right
page-margin box is allowed to cross the center of the page box.</p>

<p><img alt="Header Example 3" src="header-ex-3.png" height="177" width="737"></p>
</div>

<div class="example">

<p>The following is an example of a page with a top-center and a top-left header:</p>
<pre>
@page {
@top-left { content: "Left Cell (top-left)" }
@top-center { content: "Header in Center Cell (top-center)" }
}
</pre>

<p><img alt="Header Example 4" src="header-ex-4.png" height="177" width="737"></p>
</div>

<div class="example">

<p>The following is an example of a page with a top-center and a top-right header:</p>
<pre>
@page {
@top-center { content: "Header in Center Cell (top-center)" }
@top-right { content: "Right Cell (top-right)" }
}
</pre>

<p><img alt="Header Example 5" src="header-ex-5.png" height="177" width="737"></p>
</div>

<div class="example">

<p>The following is an example of a page with top-left and top-right headers:</p>
<pre>
@page {
@top-left { content: "Header in top-left with approx. "
                   "twice as many words as right cell." }
@top-right { content: "Right cell (top-right)" }
}
</pre>

<p>Because there are no center cell contents, the extent of the top-left is
allowed to cross the center of the page box.</p>

<p><img alt="Header Example 6" src="header-ex-6.png" height="177" width="737"></p>
</div>

<h2 id="page-properties">Page Properties</h2>
<div>

<p>
  <a href="#properties-list">Appendix A</a> defines the normative list of
  CSS 2.1 [[!CSS21]]
  <a href="#page-property-list">properties that apply to page boxes</a>.
  If a conforming user agent supports any of these properties on block boxes,
  then it <em class="RFC2119">MUST</em> also support that property
  in the <i>page context</i>.
  This specification additionally defines the 'size' property
  that only applies in the page context.

<p>
  Properties that apply to the page-margin boxes can also be set
  within the page context:
  if inheritable or explicitly inherited
  (with the ''inherit'' keyword in the margin context),
  they will inherit to the page-margin boxes.

<p>
  The same appendix defines the normative list of
  CSS 2.1 [[!CSS21]]
  <a href="#page-property-list">properties that apply to page-margin boxes</a>.
  If a conforming user agent supports any of these properties on block boxes,
  then it <em class="RFC2119">MUST</em> also support that property
  in the <i>margin context</i>.

<p>
  Other properties defined by [[!CSS21]] do not apply in these contexts.
  Behavior for properties not included in CSS 2.1 is undefined.

<p class="note">
Note: The intent of leaving other properties undefined is to allow the gradual
addition of appropriate CSS3 properties as they emerge, without having to
update this specification with each addition.</p>

<p><a href="http://www.w3.org/TR/CSS21/cascade.html#value-stages">As with
elements in the document</a>, both the page context and the margin context
have a computed value for every property, even if that property does not
apply to the page or page-margin box.</p>

<p>The normal rules for CSS properties apply with the following exceptions:</p>

<ul>
  <li>page-margin boxes inherit from the page context.
  The page context inherits from the root element.
  However, since the previous revision of CSS Paged
  Media Level 3 did not specify this point, an implementation that sets
  inherited properties in the page context to their initial values (as for the
  root element) is also conformant to CSS Paged Media Level 3. Note that this
  exception will be removed in Level 4.
  <li>Values in units of ''em'' and ''ex'' are interpreted relative to the font
  associated with their context. When used on the 'font-size' property in the
  margin context, they are relative to the font of the page context. When used
  on the 'font-size' property in the page context, they are relative to the
  'font-size' of the root element. However, since a previous revision of CSS
  Paged Media Level 3 was ambiguous on this point, an implementation that
  treats ''em'' and ''ex'' on 'font-size' as relative to the initial value is
  also conformant to CSS Paged Media Level 3. Note that this exception will
  be removed in Level 4.
  <li>Percentage values on the margin and padding properties are relative to the
  dimensions of the containing block. For right and left values, percentages are
  relative to the width of the containing block; for top and bottom values,
  percentages are relative to the height of the containing block.</li>
  <li>The used values of 'width' and 'height' have special computation rules
  for page boxes and page-margin boxes; see <a href="#page-size">Page Size</a>
  and <a href="#margin-dimension">Computing Page-Margin Box Dimensions</a>.
  <li>The page background is positioned and painted
    <a href="#painting">as described above</a>.
  <li>The rules for counter scoping are modified <a href="#page-based-counters">as
  described below</a>.</li>
  <li>
    As on the '::before' and '::after' pseudo-elements,
    the ''normal'' value of the 'content' property computes to ''none''
    on page-margin boxes.
  </li>
  <li>On page-margin boxes, the 'vertical-align' property behaves
  <a href="http://www.w3.org/TR/CSS21/tables.html#height-layout">as specified for table cells</a>.
  It <em>always</em> performs alignment in the vertical dimension,
  regardless of writing mode.
</ul>

<p>It is <em class="RFC2119">recommended</em> that user agents establish a default
page margin via the user agent stylesheet that includes any non-printable area.
It is further <em class="RFC2119">recommended</em> that authors assume that the
default page area will not include unprintable regions.</p>

<h3 id="page-based-counters">Page-based counters</h3>

<p>Counters can be defined and controlled within an ''@page''
rule, and used as content in page-margin boxes.
This is useful for maintaining a page count.</p>

<p>A 'counter-increment' within either a page or margin context causes the counter
to increment with the generation of each page box.</p>

<p>If a counter is reset or incremented within the page context, it is in scope
for all page-margin boxes and obscures all counters of the same name within the
document.</p>

<p>If a counter is reset or incremented within a margin context, it is in scope
for that page-margin box and obscures any counters of the same name
in both the page context and the document.</p>

<p>If a counter that has not been reset or incremented within the margin context
or the page context is used by counter() or counters() in the margin context,
then the resultant value is exactly
as if the page-margin box were an element within
the document at the start of the page, inside the deepest element in the normal
flow that spans the page break. Use of the counter in this way does not affect
the calculation of the counter's value.</p>

<p>
  A counter named ''page'' is automatically created
  and incremented by 1 on every page of the document,
  unless the 'counter-increment' property in the <i>page context</i>
  explicitly specifies a different increment for the ''page'' counter.
  The implied ''page'' counter is a real counter,
  and can be directly affected using the 'counter-increment' and 'counter-reset' properties
  when named explicitly in those properties.
  It can also be used in the 'counter()' and 'counters()' function forms.
</p>

<div class="example">
<p>The following rules result in the placement of the current page number in the
middle of the outside margin of each page.</p>
<pre>
@page {
  margin: 10%;

  @top-center {
    font-family: sans-serif;
    font-weight: bold;
    font-size: 2em;
    content: counter(page);
  }
}
</pre>

<p>Adding the following rule will make all pages even-numbered.</p>
<pre>
@page {
  counter-increment: page 2;
}
</pre>
</div>

<p>Additionally, a counter named ''pages'' is automatically created by the UA.
Its value is always the total number of pages in the document. (In continuous
media this is always 1.) The value of ''pages'' cannot be manipulated: while
'counter-reset' and 'counter-increment' statements that set it are valid, they
have no effect.

  <p>In all other respects, page-associated counters behave as described
    in [[!CSS21]],
    <a href="http://www.w3.org/TR/CSS21/generate.html#scope">Nested Counters
    and Scope</a> and
    <a href="http://www.w3.org/TR/CSS21/syndata.html#counter">Counters</a>.

<h3 id="margin-text-alignment">Page-margin boxes and default values</h3>

<p>Properties used within page or margin contexts take their initial values from
their respective property definitions; however, user agents must behave as
though the values in the following table were established by rules in the UA
default style sheet.</p>
<table id="margin-values" class="data" summary="definition of page-margin box default properties">
  <caption>Table 2. Default values for Page-Margin Boxes</caption>
  <thead>
    <tr>
      <th>Page-margin box</th>
      <th><span class="property">'text-align'</span></th>
      <th><span class="property">'vertical-align'</span></th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td><a href="#top-left-corner-box-def">top-left-corner</a></td>
      <td>right</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#top-left-box-def">top-left</a></td>
      <td>left</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#top-center-box-def">top-center</a></td>
      <td>center</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#top-right-box-def">top-right</a></td>
      <td>right</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#top-right-corner-box-def">top-right-corner</a></td>
      <td>left</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#left-top-box-def">left-top</a></td>
      <td>center</td>
      <td>top</td>
      </tr>
    <tr>
      <td><a href="#left-middle-box-def">left-middle</a></td>
      <td>center</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#left-bottom-box-def">left-bottom</a></td>
      <td>center</td>
      <td>bottom</td>
      </tr>
    <tr>
      <td><a href="#right-top-box-def">right-top</a></td>
      <td>center</td>
      <td>top</td>
      </tr>
    <tr>
      <td><a href="#right-middle-box-def">right-middle</a></td>
      <td>center</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#right-bottom-box-def">right-bottom</a></td>
      <td>center</td>
      <td>bottom</td>
      </tr>
    <tr>
      <td><a href="#bottom-left-corner-box-def">bottom-left-corner</a></td>
      <td>right</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#bottom-left-box-def">bottom-left</a></td>
      <td>left</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#bottom-center-box-def">bottom-center</a></td>
      <td>center</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#bottom-right-box-def">bottom-right</a></td>
      <td>right</td>
      <td>middle</td>
      </tr>
    <tr>
      <td><a href="#bottom-right-corner-box-def">bottom-right-corner</a></td>
      <td>left</td>
      <td>middle</td>
    </tr>
  </tbody>
</table>

<div class="example">

<p>This example style sheet could be used to create a centered header with the
current chapter name:</p>
<pre>body {counter-reset: chapter;}
div.chapter {counter-increment: chapter;}
@page {
margin: 10%;
@top-center { content: "Chapter" counter(chapter) }
}
</pre>
</div>

<h2 id="page-size">Page Size</h2>

<p>People around the world use many different paper sizes. It is a goal of this
specification that web content should be adaptable to a range of different
sizes without having to write a specific style sheet for each paper size.</p>

<p>However, in some situations it is important that a certain page size achieves a
certain style. One way to achieve this goal is to utilize the 'size' property,
which indicates that the document should preferentially be displayed on a
surface of a certain size; another method is to use Media Queries [[MEDIAQ]]
which allow different style sheets to be applied to different page sizes.</p>

<h3 id="page-size-prop">Page size: the 'size' property</h3>

<table class="propdef" summary="definition of the size property">
  <tr>
    <th>Name:
    <td><dfn id="size">size</dfn>
  <tr>
    <th>Value:
    <td>&lt;length&gt;{1,2} | auto | [ &lt;page-size&gt; || [ portrait | landscape] ]
  <tr>
    <th>Initial:
    <td>auto
  <tr>
    <td><em>Applies to:</em>
    <td>page context
  <tr>
    <th>Inherited:
    <td>N/A
  <tr>
    <th>Percentages:
    <td>N/A
  <tr>
    <th>Media:
    <td>paged
  <tr>
    <td><em>Computed value:</em>
    <td>specified value
</table>

<p>This property specifies the target size and orientation of the
<a href="#page-box">page box</a>’s containing block.
In the general case, where one page box is rendered onto one <a href="#page-sheet">page sheet</a>,
the 'size' property also indicates the size of the destination page sheet.

<p>The size of a page box can either be "absolute" (fixed size) or "scalable"
(i.e., fitting available sheet sizes).
The first three values in the table below can be used to create scalable page
boxes.
Other values define a fixed-size page box, and thereby indicate the preferred
output media size. When possible, output should be rendered on the media size
indicated.
If the specified size is not available, the rules for
<a href="#renderingpages">transposing a page box to a different size</a>
apply.</p>

<p>If a <code>size</code> property declaration is qualified by a ''width'',
''height'', ''device-width'', ''device-height'', ''aspect-ratio'',
''device-aspect-ratio'' or ''orientation''
media query [[!MEDIAQ]] (or other conditional on the size of the paper), then
the declaration must be
<a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignored</a>. Media
queries do not honor 'size': they assume the paper size that would be chosen
if no @page rules were specified.</p>

<div class=issue>
  <p>It would be useful if media queries could respond at least
  to sizes specified on an unqualified @page.

  <p>Another option could be to do like ''@viewport'' rules
  [[CSS-DEVICE-ADAPT]]:
  First apply ''@page'' rules (matching which selectors?),
  using the UA’s default page size for Media Queries and
  <a href="http://www.w3.org/TR/css3-values/#viewport-relative-lengths">viewport-percentage lengths</a>
  [[CSS3VAL]].
  The resulting page size is the "base page size".
  The entire set of stylesheets is applied again,
  this time using the "base page size" for Media Queries
  and viewport-percentage lengths.
</div>


<div class="example">
  <p>In the following example
  <pre>
  @page {
    size: 4in 6in;
  }

  @media (max-width: 6in) {
    @page {
      size: letter;
    }
  }
  </pre>
  <p>The second <code>size</code> declaration is ignored, i.e. the specified value
  of the <code>size</code> property is <code>4in 6in</code>.
</div>

<table class="page-sizes">
<tr>
<th>Value</th>
<th>Description</th>
</tr>
<tr>
<td>auto</td>
<td>The page box will be set to a size and orientation chosen by the UA. In the
usual case, the page box size and orientation is chosen to match the target
media sheet.</td>
</tr>
<tr>
<td>landscape</td>
<td>Specifies that the page's content be printed in landscape orientation. The
longer sides of the page box are horizontal. If a <<page-size>> is not specified, the size of the page sheet
is chosen by the UA.</td>
</tr>
<tr>
<td>portrait</td>
<td>Specifies that the page's content be printed in portrait orientation. The
shorter sides of the page box are horizontal. If a <<page-size>> is not specified, the size of the page sheet
is chosen by the UA.</td>
</tr>
<tr>
<td>&lt;length&gt;</td>
<td>The page box will be set to the given absolute dimension(s). If only one length
value is specified, it sets both the width and height of the page box (i.e.,
the box is a square). If two length values are specified, the first establishes
the page box width, and the second the page box height. Values in units of
''em'' and ''ex'' refer to the
page context's font. Negative lengths are illegal.</td>
</tr>
<tr>
<td><dfn><<page-size>></dfn></td>
<td>A page size can be specified using one of the following media names. This is
the equivalent of specifying 'size'
using length values. The definition of the the media names comes from
<cite>Media Standardized Names</cite> [[!PWGMSN]].

<dl>

<dt>A5</dt>
<dd>Equivalent to the size of ISO A5 media: 148mm wide and 210 mm high.</dd>

<dt>A4</dt>
<dd>Equivalent to the size of ISO A4 media: 210 mm wide and 297 mm high.</dd>

<dt>A3</dt>
<dd>Equivalent to the size of ISO A3 media: 297mm wide and 420mm high.</dd>

<dt>B5</dt>
<dd>Equivalent to the size of ISO B5 media: 176mm wide by 250mm high.</dd>

<dt>B4</dt>
<dd>Equivalent to the size of ISO B4 media: 250mm wide by 353mm high.</dd>

<dt>letter</dt>
<dd>Equivalent to the size of North American letter media: 8.5 inches wide and 11
inches high</dd>

<dt>legal</dt>
<dd>Equivalent to the size of North American legal: 8.5 inches wide by 14 inches
high.</dd>

<dt>ledger</dt>
<dd>Equivalent to the size of North American ledger: 11 inches wide by 17 inches
high.</dd>
</dl></td>
</tr>
</table>

<p>The <<page-size>> names can be used in conjunction with ''landscape'' or
''portrait'' to indicate both size and orientation.</p>

<div class="example">
<pre>
@page {
size: A4 landscape;
}
</pre>

<p>The above example sets the width of the page box to be 297mm and the height to
be 210mm. The page box in this example should be rendered on a page sheet size
of 210 mm by 297 mm.</p>
</div>

<div class="example">

<p>In the following example, the outer edges of the page box will align with the
page. The percentage value on the <span class="property">'margin'</span>
property is relative to the page size so if the page sheet dimensions are 210mm
x 297mm (i.e., A4), the margins are 21mm and 29.7mm. Assuming there are no page
borders or padding set in the UA default style sheet, the resulting page area
is 189mm by 367.3mm (210mm-21mm by 297mm-29.7mm).</p>
<pre>
@page {
size: auto;/* auto is the initial value */
margin: 10%;
}
</pre>
</div>

<div class="example">
<pre>
@page {
size: 8.5in 11in;/* width height */
}
</pre>

<p>The above example sets the width of the page box to be 8.5 inches and the
height to be 11 inches. This indicates that the page sheet size should be
8.5"x11" and the orientation ''portrait''.</p>
</div>

<h4 id="page-size-media-query">Media Queries</h4>

<p>This section is informative.</p>

<p>By using Media Queries [[MEDIAQ]], one style sheet can express different
stylistic preferences for different page sizes. Consider this example:</p>

<div class="example" style="font-size: 10pt;">
<pre>
 /* style sheet for "A4" printing */
 @media print and (width: 21cm) and (height: 29.7cm) {
    @page {
       margin: 3cm;
    }
 }

 /* style sheet for "letter" printing */
 @media print and (width: 8.5in) and (height: 11in) {
    @page {
        margin: 1in;
    }
 }
</pre>
</div>

<p>In the example above, "A4" sheets are given a "3cm" page margin, and "letter"
sheets are given a "1in" page margin.</p>


<h3 id="page-marks-bleed">Page marks and bleed area</h3>

<p>The 'marks' property from [[CSS2]] is part of this specification.

<pre class='propdef'>
Name: marks
Value: [ crop || cross ] | none
Initial: none
Applies To: page context
Inherited: no
Computed Value: as specified
Media: visual, paged
</pre>

<p>This property adds crop and/or cross marks to the document. Crop
marks indicate where the page should be cut. Cross marks are used to
align sheets.

<p>Crop marks and cross marks are printed outside the page box. To
have room to show crop and cross marks, the final pages will have to
be somewhat bigger than the page box.

<div class="example">
<p>To set crop and cross marks on a document, this code can be used:
<pre>
@page { marks: crop cross }
</pre>
</div>

<pre class='propdef'>
Name: bleed
Value: <<length>>
Initial: 6pt
Applies To: page context
Inherited: no
Percentages: refer to width of page box
Computed Value: as specified
Media: visual, paged
</pre>

<p>This property specifies the extent of the page bleed area outside
the page box. This property only has effect if crop marks are enabled.


<h3 id="renderingpages">Rendering page boxes that do not fit a page sheet</h3>

<p>If a page box does not match the target page sheet dimensions, the user agent
should do one of the following (in order of preference):</p>

<ol>
  <li>Render the page box at the indicated size on a larger page sheet.</li>
  <li>Rotate the page box 90° if this will make the page box fit the page sheet.</li>
  <li>Scale the page box to fit the page sheet. (The aspect ratio of the page box
  <em class="RFC2119">should</em> be preserved.)</li>
  <li>Graphically "slice" the page box onto multiple page sheets.</li>
  <li>Clip overflowed content (least preferred).</li>
</ol>

<p>The user agent <em class="RFC2119">MAY</em> wish to consult the user before
performing these operations.</p>

<h3 id="positioning-page-box">Positioning the page box on the sheet</h3>

<p>When the page box is smaller than the page sheet, the user agent <em class="RFC2119">SHOULD</em> either:</p>

<ul>
  <li>center the page box on the sheet since this will align double-sided pages
  and avoid accidental loss of information that is printed near the edge of the
  sheet; or</li>
  <li>position the page box in the upper left corner of the page sheet
  (or another corner,
  based on the 'direction' and 'writing-mode' properties of the page box)
  as this may minimize media consumption.</li>
</ul>

<p>The user agent <em class="RFC2119">MAY</em> wish to consult the user in this
regard.</p><!-- "Page selector and page context" -->

<h2 id="page-breaks">
    <span id="pg-br-before-after"></span>
    <span id="page-break-before"></span>
    <span id="page-break-after"></span>
    <span id="page-break-inside"></span>
    <span id="breaks-inside"></span>
    <span id="orphans"></span>
    <span id="widows"></span>
    <span id="allowed-pg-brk"></span>
    <span id="brk-btw-blocks"></span>
    <span id="brk-btw-lines"></span>
    <span id="brk-end-block"></span>
    <span id="forced-pg-brk"></span>
    <span id="best-pg-brk"></span>
    Page Breaks
</h2>

<p>
  The CSS Fragmentation Module [[!CSS3-BREAK]] module
  defines how and where CSS boxes
  can be <em>fragmented</em>, including across page breaks.
  It defines a few properties that indicate where the user agent
  <em class="RFC2119">MAY</em> or <em class="RFC2119">MUST</em> break pages,
  and on what page (left or right) the subsequent content resumes.
  Each page break ends layout in the current <a href="#page-box">page box</a>
  and causes remaining pieces of the document tree to be laid out
  in a new page box.
</p>

<h3 id="using-named-pages">Using named pages: 'page'</h3>
<table class="propdef" summary="property definition">
  <tr>
    <th>Name:
    <td><dfn id="page">page</dfn>
  <tr>
    <th>Value:
    <td>auto | &lt;identifier&gt;
  <tr>
    <th>Initial:
    <td>auto
  <tr>
    <th>Applies to:
    <td>boxes that create <a href="http://www.w3.org/TR/css3-break/#btw-blocks">class A</a> break points
  <tr>
    <th>Inherited:
    <td>no (but see prose)
  <tr>
    <th>Percentages:
    <td>N/A
  <tr>
    <th>Media:
    <td>paged
  <tr>
    <th>Computed value:
    <td>specified value
</table>

<p>
  The 'page' property is used to specify a particular type of page (called a <dfn>named page</dfn>)
  on which an element <em class="RFC2119">MUST</em> be displayed.
  If necessary, a <i title="forced break" spec=css-break>forced page break</i> is introduced
  and a new page generated of the specified type.

<p class="note">
  This page can be styled by using the same type name
  in a <a href="#page-selectors">page selector</a>.

<p>
  Page type names are case-sensitive identifiers.
  However the ''auto'' value, being a CSS keyword, is
  <a href="http://www.w3.org/TR/CSS21/syndata.html#characters">ASCII case-insensitive</a>.

<p>
  The 'page' property does not inherit.
  However, if the 'page' value on an element is ''auto'',
  then its used value is the value specified
  on its nearest ancestor with a non-auto value.
  When specified on the root element,
  the used value for ''auto'' is the empty string.

  <!-- See http://www.w3.org/TR/2007/WD-css3-gcpm-20070504/#named3 -->

<p>
  Because a previous version of this specification
  indicated that the 'page' property is inherited,
  an implementation that inherits the 'page' property
  and treats ''auto'' as always naming the empty string
  remains conformant to CSS Paged Media Level 3.
  Note that this exception will be removed in Level 4.
  Therefore authors should not explicitly specify the ''auto'' value
  on a descendant of an element with a non-''auto'' value,
  as the resulting behavior will be unpredictable.

<p>
  The 'page' property works as follows:

<ol>

  <li>
    First, any ''auto'' values are resolved against non-''auto'' ancestors
    (as specified above).

  <li>
    Next,
    a <dfn>start 'page' value</dfn> and <dfn>end 'page' value</dfn>
    is determined for each box
    as the value (if any) propagated from
    its first or last child box (respectively),
    else the used value on the box itself.
    A child propagates its own
    <i title="start page value">start</i> or <i>end 'page' value</i>
    if and only if the 'page' property applies to it.

    <p class="note">
      Note:
      A first or last child <em>box</em> is not always generated by
      a first or last child <em>element</em>.
      For example,
      an element could only have a previous sibling with 'display: none'
      which does not generate any box.

  <li>
    The first printed page’s type is the <i>start 'page' value</i> of the root.

  <li>
    If for any two boxes meeting at a <a href="http://www.w3.org/TR/css3-break/#btw-blocks">class A</a> break point,
    the <i>end 'page' value</i> of the box preceding the break
    and <i>start 'page' value</i> of the box succeeding the break
    do not match,
    then a page break is forced between the two boxes,
    and content after the break resumes on a page box of the named type.
</ol>

<p class="note">
  Essentially, the two 'page' values compared are those from the deepest boxes
  meeting at the <a href="http://www.w3.org/TR/css3-break/#btw-blocks">class A break point</a>,
  ignoring any subtrees rooted by boxes to which the 'page' property does not apply.

<p>See [[!CSS3-BREAK]] for additional details on page breaks.

<div class="example">

<p>In this example, the two tables are rendered on landscape pages (indeed, on the
same page, if they fit). The page type "narrow" is used for the &lt;p&gt; after
the second table, as the page properties for the table element are no longer in
effect:</p>
<pre>
@page narrow { size: 9cm 18cm }
@page rotated { size: landscape }
div { page: narrow }
table { page: rotated }
</pre>with this document:
<pre>
&lt;div&gt;
&lt;table&gt;...&lt;/table&gt;
&lt;table&gt;...&lt;/table&gt;
&lt;p&gt;This text is rendered on a 'narrow' page&lt;/p&gt;
&lt;/div&gt;
</pre>
</div>

<div class="example">
  <p>In Japanese documents, sometimes different parts of a single document
  will have different <em lang="ja-Latn">kihon hanmen</em>. [[JLREQ]]
  The 'page' property, together with ''@page'' rules specifying different page widths,
  can accomodate this type of layout:
  <pre>
&lt;!DOCTYPE html>
&lt;html lang="ja">
  &lt;style>
    html   { writing-mode: vertical-rl;
             line-height: 1.6; }
    .main  { page: main;
             columns: 2; column-gap: 1rem; }
    .index { page: index;
             columns: 3; column-gap: 1rem; }
    @page       { margin: auto;    /* center kihon hanmen on page */
                  width:  40rem; } /* 1.6 &times; 25 lines        */
    @page main  { height: 61rem; } /* 2 &times; 30 chars + 1 &times; gap */
    @page index { height: 62rem; } /* 3 &times; 20 chars + 2 &times; gap */
  &lt;/style>
  &lt;section class="main"> ... &lt;/section>
  &lt;section class="index"> ... &lt;/section>
&lt;/html>
</pre>
</div>


<h2 id="image-properties">Image Properties</h2>

<p class="note">This section has been moved to [[CSS3-IMAGES]].</p>

<h2 class="no-num" id="properties-list">Appendix A: Applicable CSS2.1 Properties</h2>

<h3 class="no-num" id="page-property-list">
  CSS 2.1 Properties that apply within the page context</h3>

<p>
  This list is described in the
  <a href="#page-properties">Page Properties</a> section.

<table class="property-list">
  <tbody>
    <tr><td rowspan="2"><a href="http://www.w3.org/TR/CSS21/visuren.html#direction">bidi properties</a>
        <td>direction
  <tbody>
    <tr><td rowspan="6"><a href="http://www.w3.org/TR/CSS21/colors.html#background-properties">background properties</a>
        <td>background-color
    <tr><td>background-image
    <tr><td>background-repeat
    <tr><td>background-attachment
    <tr><td>background-position
    <tr><td>background
  <tbody>
    <tr><td rowspan="20"><a href="http://www.w3.org/TR/CSS21/box.html#border-properties">border properties</a>
        <td>border-top-width
    <tr><td>border-right-width
    <tr><td>border-bottom-width
    <tr><td>border-left-width
    <tr><td>border-width
    <tr><td>border-top-color
    <tr><td>border-right-color
    <tr><td>border-bottom-color
    <tr><td>border-left-color
    <tr><td>border-color
    <tr><td>border-top-style
    <tr><td>border-right-style
    <tr><td>border-bottom-style
    <tr><td>border-left-style
    <tr><td>border-short-style
    <tr><td>border-top
    <tr><td>border-right
    <tr><td>border-bottom
    <tr><td>border-left
    <tr><td>border
  <tbody>
    <tr><td rowspan="2"><a href="http://www.w3.org/TR/CSS21/generate.html#counters">counter properties</a>
        <td>counter-reset
    <tr><td>counter-increment
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/colors.html#propdef-color">color</a>
  <tbody>
    <tr><td rowspan="6"><a href="http://www.w3.org/TR/CSS21/fonts.html">font properties</a>
        <td>font-family
    <tr><td>font-size
    <tr><td>font-style
    <tr><td>font-variant
    <tr><td>font-weight
    <tr><td>font
  <tbody>
    <tr><td rowspan="3"><a href="http://www.w3.org/TR/CSS21/visudet.html#the-height-property">height</a> <a href="http://www.w3.org/TR/CSS21/visudet.html#min-max-heights">properties</a>
        <td>height
    <tr><td>min-height
    <tr><td>max-height
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/visudet.html#line-height">line-height</a>
  <tbody>
    <tr><td rowspan="5"><a href="http://www.w3.org/TR/CSS21/box.html#margin-properties">margin properties</a>
        <td>margin-top
    <tr><td>margin-right
    <tr><td>margin-bottom
    <tr><td>margin-left
    <tr><td>margin
  <tbody>
    <tr><td rowspan="5"><a href="http://www.w3.org/TR/CSS21/ui.html#dynamic-outlines">outline properties</a>
        <td>outline-width
    <tr><td>outline-style
    <tr><td>outline-color
    <tr><td>outline
  <tbody>
    <tr><td rowspan="5"><a href="http://www.w3.org/TR/CSS21/box.html#padding-properties">padding properties</a>
        <td>padding-top
    <tr><td>padding-right
    <tr><td>padding-bottom
    <tr><td>padding-left
    <tr><td>padding
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/generate.html#quotes-specify">quotes</a>
  <tbody>
    <tr><td rowspan="7"><a href="http://www.w3.org/TR/CSS21/text.html">text properties</a>
        <td>letter-spacing
    <tr><td>text-align
    <tr><td>text-decoration
    <tr><td>text-indent
    <tr><td>text-transform
    <tr><td>white-space
    <tr><td>word-spacing
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/visufx.html#visibility">visibility</a>
  <tbody>
    <tr><td rowspan="3"><a href="http://www.w3.org/TR/CSS21/visudet.html#the-width-property">width</a> <a href="http://www.w3.org/TR/CSS21/visudet.html#min-max-widths">properties</a>
        <td>width
    <tr><td>min-width
    <tr><td>max-width
</table>


<h3 class="no-num" id="margin-property-list">
  CSS 2.1 properties that apply within the margin contexts</h3>

<p>
  This list is described in the
  <a href="#page-properties">Page Properties</a> section.

<table class="property-list">
  <tbody>
    <tr><td rowspan="2"><a href="http://www.w3.org/TR/CSS21/visuren.html#direction">bidi properties</a>
        <td>direction
    <tr><td>unicode-bidi
  <tbody>
    <tr><td rowspan="6"><a href="http://www.w3.org/TR/CSS21/colors.html#background-properties">background properties</a>
        <td>background-color
    <tr><td>background-image
    <tr><td>background-repeat
    <tr><td>background-attachment
    <tr><td>background-position
    <tr><td>background
  <tbody>
    <tr><td rowspan="20"><a href="http://www.w3.org/TR/CSS21/box.html#border-properties">border properties</a>
        <td>border-top-width
    <tr><td>border-right-width
    <tr><td>border-bottom-width
    <tr><td>border-left-width
    <tr><td>border-width
    <tr><td>border-top-color
    <tr><td>border-right-color
    <tr><td>border-bottom-color
    <tr><td>border-left-color
    <tr><td>border-color
    <tr><td>border-top-style
    <tr><td>border-right-style
    <tr><td>border-bottom-style
    <tr><td>border-left-style
    <tr><td>border-short-style
    <tr><td>border-top
    <tr><td>border-right
    <tr><td>border-bottom
    <tr><td>border-left
    <tr><td>border
  <tbody>
    <tr><td rowspan="2"><a href="http://www.w3.org/TR/CSS21/generate.html#counters">counter properties</a>
        <td>counter-reset
    <tr><td>counter-increment
  <tbody>
    <tr><td colspan="2"><a href="">content</a>
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/colors.html#propdef-color">color</a>
  <tbody>
    <tr><td rowspan="6"><a href="http://www.w3.org/TR/CSS21/fonts.html">font properties</a>
        <td>font-family
    <tr><td>font-size
    <tr><td>font-style
    <tr><td>font-variant
    <tr><td>font-weight
    <tr><td>font
  <tbody>
    <tr><td rowspan="3"><a href="http://www.w3.org/TR/CSS21/visudet.html#the-height-property">height</a> <a href="http://www.w3.org/TR/CSS21/visudet.html#min-max-heights">properties</a>
        <td>height
    <tr><td>min-height
    <tr><td>max-height
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/visudet.html#line-height">line-height</a>
  <tbody>
    <tr><td rowspan="5"><a href="http://www.w3.org/TR/CSS21/box.html#margin-properties">margin properties</a>
        <td>margin-top
    <tr><td>margin-right
    <tr><td>margin-bottom
    <tr><td>margin-left
    <tr><td>margin
  <tbody>
    <tr><td rowspan="5"><a href="http://www.w3.org/TR/CSS21/ui.html#dynamic-outlines">outline properties</a>
        <td>outline-width
    <tr><td>outline-style
    <tr><td>outline-color
    <tr><td>outline
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/visufx.html#overflow">overflow</a>
  <tbody>
    <tr><td rowspan="5"><a href="http://www.w3.org/TR/CSS21/box.html#padding-properties">padding properties</a>
        <td>padding-top
    <tr><td>padding-right
    <tr><td>padding-bottom
    <tr><td>padding-left
    <tr><td>padding
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/generate.html#quotes-specify">quotes</a>
  <tbody>
    <tr><td rowspan="7"><a href="http://www.w3.org/TR/CSS21/text.html">text properties</a>
        <td>letter-spacing
    <tr><td>text-align
    <tr><td>text-decoration
    <tr><td>text-indent
    <tr><td>text-transform
    <tr><td>white-space
    <tr><td>word-spacing
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/visudet.html#line-height">vertical-align</a>
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/visufx.html#visibility">visibility</a>
  <tbody>
    <tr><td rowspan="3"><a href="http://www.w3.org/TR/CSS21/visudet.html#the-width-property">width</a> <a href="http://www.w3.org/TR/CSS21/visudet.html#min-max-widths">properties</a>
        <td>width
    <tr><td>min-width
    <tr><td>max-width
  <tbody>
    <tr><td colspan="2"><a href="http://www.w3.org/TR/CSS21/visuren.html#z-index">z-index</a>
</table>

<h2 class="no-num" id="transfer-possibilities">Appendix B: Transfer Possibilities</h2>

<p>Often, but not always, the page box has a one-to-one correspondence to the
physical surface onto which the document is ultimately rendered. The CSS3 page
model specifies formatting within the page box, but it is the user agent's
responsibility to transfer the page box to the sheet. Some user agent transfer
possibilities that are not addressed by CSS3 include:</p>

<ul id="complex-usecases">
  <li>Transferring one page box to one sheet (e.g. single-sided printing);</li>
  <li>Transferring two page boxes to the front and back surfaces of the same
  sheet (e.g. double-sided printing);</li>
  <li>Transferring N (small) page boxes to one sheet (called "N-up");</li>
  <li>Transferring one (large) page box to N x M sheets (called "tiling");</li>
  <li>Creating signatures. A <dfn>signature</dfn> is a group of pages printed on
  a sheet, which, when folded and trimmed like a book, appear in their proper
  sequence;</li>
  <li>Printing one document to multiple output trays;</li>
  <li>Generating files containing print instructions.</li>
</ul>

<h2 class="no-num" id="changes">Changes</h2>

<p>
  Changes since the <a href="http://www.w3.org/TR/2006/WD-css3-page-20061010/">10 October 2006 Working Draft</a> are:
</p>

<ul>
  <li>The first printed page can be <a href="#using-named-pages">named</a>.

  <li>The '':blank'' pseudo-class was imported
    from the <a href="http://dev.w3.org/csswg/css3-gcpm/">Generated Content for Paged Media</a> module.

  <li>''@page'' rules can now take multiple comma separated selectors,
    each selector can have multiple pseudo-classes.

    <div class="example">
      <pre>@page :first, :blank { @bottom-center { content: none } }</pre>
      <pre>@page :first:left { @bottom-left { content: none } }</pre>
    </div>

  <li>Margin boxes are renamed <a href="#margin-boxes">page-margin boxes</a>,
    to avoid confusion with the margin area of each box.

  <li>The <a href="#variable-sizing">Variable Dimension</a>
    layout rules for page-margin boxes have been much simplified
    to not require quadratic optimization.

  <li>The relative <a href="#painting">painting order</a>
    of page-margin boxes and page content has changed.

  <li>The description of page breaks and definition of related properties
    (except for the 'page' property)
    have been moved to the CSS Fragmentation Module. [[!CSS3-BREAK]]

  <li>The 'fit' and 'fit-position' properties
    are renamed to 'object-fit' and 'object-position',
    redefined to enable additional use cases,
    and moved to the CSS3 Image Values and Replaced Content module.
    [[CSS3-IMAGES]]

  <li>The default stacking order of page-magin boxes is now defined.

  <li>Support for the 'z-index' property on page-margin boxes
    is not optional anymore.

  <li>Each page-margin box eastablishes a stacking context.

  <li>Many miscellaneous clarifications
    and editorial improvements have been incorporated.

</ul>