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<!DOCTYPE html>
<html><head>
<title>CSS Lists and Counters Module Level 3</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" >
<link rel="stylesheet" type="text/css" href="http://dev.w3.org/csswg/default.css">
<style>
code.inline { white-space: nowrap; }
.alphabetic-example { font-family: monospace; font-size: 90%; margin: 1em 0 1em 2em; }
.alphabetic-example > span { display: inline-block; width: 50px;}
.alphabetic-example > span > img { width: 16px; height: 16px; }
pre > code { white-space: pre-wrap; }
.nobr { white-space: nowrap;}
</style>
<link rel="stylesheet" type="text/css" href="http://www.w3.org/StyleSheets/TR/W3C-ED">
</head><body>
<div class="head">
<!--logo-->
<h1>CSS Lists and Counters Module Level 3</h1>
<h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
<dl>
<dt>This version:
<dd><!--<a href="http://www.w3.org/TR/[YEAR]/WD-[SHORTNAME]-[CDATE]">http://www.w3.org/TR/[YEAR]/WD-[SHORTNAME]-[CDATE]</a></dd>-->
<a href="http://dev.w3.org/csswg/css3-lists/">http://dev.w3.org/csswg/css3-lists/</a></dd>
<dt>Latest version:
<dd><a href="http://www.w3.org/TR/css3-lists/">http://www.w3.org/TR/css3-lists/</a></dd>
<dt>Previous version:</dt>
<dd><a href="http://www.w3.org/TR/2002/WD-css3-lists-20021107/">http://www.w3.org/TR/2002/WD-css3-lists-20021107/</a></dd>
<dt>Editor:</dt>
<dd><a href="http://www.xanthir.com/contact">Tab Atkins Jr.</a>, Google Inc.</dd>
<dt>Previous Editors:</dt> <!-- in the order tantek requested -->
<dd>Ian Hickson, <a href="mailto:ian@hixie.ch">ian@hixie.ch</a></dd>
<dd><span lang="tr">Tantek Çelı̇k</span>, Microsoft Corporation,
<a href="mailto:tantekc@microsoft.com">tantekc@microsoft.com</a></dd>
<dt>Contributors:</dt> <!-- in order of volume of input -->
<dd>Simon Montagu, AOL-TW/Netscape, <a href="mailto:smontagu@netscape.com">smontagu@netscape.com</a></dd>
<dd>Daniel Yacob, <a href="mailto:yacob@geez.org">yacob@geez.org</a></dd>
<dd>Christopher Hoess, <a href="mailto:choess@stwing.upenn.edu">choess@stwing.upenn.edu</a></dd>
<dd>Daniel Glazman, AOL-TW/Netscape, <a href="mailto:glazman@netscape.com">glazman@netscape.com</a></dd>
</dl>
<!--copyright-->
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc" id="abstract">
Abstract</h2>
<p>CSS is a language for describing the rendering of structured documents
(such as HTML and XML) on screen, on paper, in speech, etc.
This draft contains the features of CSS level 3 relating to
list styling. It includes and extends the functionality of
CSS level 2 [[!CSS21]], which builds on CSS level 1
[[CSS1]]. The main extensions compared to level 2 are a pseudo-element
representing the list marker,
and a method for authors to define their own list-styles.</p>
<h2 class="no-num no-toc" id="status">
Status of this document</h2>
<!--status-->
<h2 class="no-num no-toc" id="contents">
Table of contents</h2>
<!--toc-->
<hr>
<!-- ====================================================================== -->
<h2>
Introduction</h2>
<p>The list model in this module differs in some important ways from the list model in CSS2,
specifically in its handling of markers. Implementation experience suggested the CSS2 model
overloaded the ::before and ::after pseudo-elements with too much behavior, while at the same time
introducing new properties when existing properties were sufficient.</p>
<p>Most block-level elements in CSS generate one principal block box. In this module, we discuss two
CSS mechanisms that cause an element to have an associated marker: one method associates one
principal block box (for the element's content) with a separate marker box (for decoration such as a
bullet, image, or number), and the other inserts a marker box into the principal box. Unlike :before
and :after content, the marker box cannot affect the position of the principal box, whatever the
positioning scheme.</p>
<div class="html-example">
<p>For instance, the following example illustrates how markers may be used to add parentheses around each numbered list item. This HTML application and style sheet:</p>
<pre>
<style>
li::marker { content: "(" counter(list-item, lower-roman) ")"; }
li { display: list-item; }
</style>
<ol>
<li>This is the first item.</li>
<li>This is the second item.</li>
<li>This is the third item.</li>
</ol></pre>
<p>should produce something like this: </p>
<pre>
(i) This is the first item.
(ii) This is the second item.
(iii) This is the third item.
</pre>
</div>
<p>With descendant selectors and child selectors, it's possible to specify different marker types depending on the depth of embedded lists.</p>
<p class="issue">A future release of this module will probably include ways to render tree
lists.</p>
<!-- ====================================================================== -->
<h2>
Declaring a List Item</h2>
<p>To declare a <dfn>list item</dfn>, the 'display'property must be set to ''list-item'' or ''inline-list-item'' (defined later in this section). This, in addition to generating a ''::marker''pseudo-element and enabling the properties described below for that element, causes that element to increment the list item counter ''list-item'': if the element doesn't otherwise have a 'counter-increment' declaration, it must act as if ''counter-increment: list-item'' were specified. (This does not affect the specified or computed values of the counter properties.)</p>
<p>The ''list-item'' counter is a real counter,
and can be directly affected using the 'counter-increment' and ''counter-reset''
properties. It can also be used in the ''counter()'' and ''counters()'' functions.</p>
<table class="propdef">
<tbody>
<tr>
<th>Property:
<td>'display'
<tr>
<th>New Value:
<td><dfn>inline-list-item</dfn>
<tr>
<th>Initial:
<td>same as CSS2.1
<tr>
<th>Applies to:
<td>same as CSS2.1
<tr>
<th>Inherited:
<td>same as CSS2.1
<tr>
<th>Percentages:
<td>same as CSS2.1
<tr>
<th>Media:
<td>same as CSS2.1
<tr>
<th>Computed value:
<td>same as CSS2.1
</tbody>
</table>
<p>The ''inline-list-item'' display value makes the element a list item,
which means it can generate a <code class=css>::marker</code> pseudo-element. The element also
affects the predefined ''list-item'' counter, as specified above. Otherwise,
this display value is treated identically to ''inline''.</p>
<p class='note'>This display value is silly, and only necessary because we
haven't yet defined 'display' to be split into subproperties. When that
happens, "being a list item" will just be a property value that can apply
to block, inline, and other elements.</p>
<!-- ====================================================================== -->
<h2 id='marker-content'>
Marker Content: The 'list-style-image' and 'list-style-type' properties</h2>
<table class="propdef">
<tr>
<th>Name:
<td><dfn>list-style-image</dfn>
<tr>
<th>Value:
<td><image> | none
<tr>
<th>Initial
<td>none
<tr>
<th>Applies To:
<td><i title="list item">list items</i>
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed Value:
<td>specified value
</table>
<p>The 'list-style-type' property specifies an image that will be used as the list marker. If the value resolves to a valid image, the image must be used as the default contents of the <code class=css>::marker</code> pseudo-element.</p>
<p>If the value ''none'' is provided, or the <i><image></i> doesn't resolve to a valid image, then the default contents are given by 'list-style-type' instead.</p>
<div class="example">
<p>The following example sets the marker at the beginning of each list item to
be the image "ellipse.png".</p>
<pre>LI { list-style-image: url("http://www.example.com/ellipse.png") }</pre>
</div>
<table class="propdef">
<tr>
<th>Name:
<td><dfn>list-style-type</dfn>
<tr>
<th>Value:
<td><string> | <counter-style> | none
<tr>
<th>Initial:
<td>disc
<tr>
<th>Applies To:
<td><i title="list item">list items</i>
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed Value:
<td>specified value
</table>
<p>When the 'list-style-image' property is ''none'' or not a valid image, the 'list-style-type' property must be used to construct the default contents of a list item's marker; otherwise, the 'list-style-type' property must be ignored and have no effect.</p>
<dl>
<dt><string></dt>
<dd>The <code class=css>::marker</code> pseudo-element must use the provided string as its default contents.</dd>
<dt><i><counter-style></i></dt>
<dd>
<p>The <code class=css>::marker</code> pseudo-element's default contents must be the value of the ''list-item'' counter, formatted according to the given counter style. Algorithms for formatting a value according to a counter style are given later in this spec.</p>
<p>This specification defines a method for authors to create their own counter styles, both <a href="#counter-style">named</a> and <a href="#symbols-function">anonymous</a>, which may be used here. Additionally, many useful counter styles are predefined in the sections on <a href="#predefined-counters">Complex Counter Styles</a> and <a href="#ua-stylesheet">Predefined Counter Styles</a>.</p>
</dd>
<dt><dfn>none</dfn></dt>
<dd>The <code class=css>::marker</code> pseudo-element must have no default contents. This will suppress the creation of a marker unless the <code class=css>::marker</code> has its contents specified directly through the 'content' property.</dd>
</dl>
<div class='example'>
<p>The following examples illustrate how to set markers to various values:</p>
<pre>
ul { list-style-type: "★"; }
/* Sets the marker to a "star" character */
p.note {
display: list-item;
list-style-type: "Note:";
list-style-position: inside;
}
/* Gives note paragraphs a marker consisting of the string "Note:" */
ol { list-style-type: upper-roman; }
/* Sets all ordered lists to use the upper-roman counter-style
(<a href="#upper-roman">defined in this specification</a>) */
ul { list-style-type: symbols('○' '●' as repeating); }
/* Sets all unordered list items to alternate between empty and
filled circles for their markers. */
ul { list-style-type: none; }
/* Suppresses the marker entirely, unless list-style-image is specified
with a valid image, or the marker's contents are set explicitly via
the 'content' property. */</pre>
</div>
<p>The <i><counter-style></i> type is defined as:</p>
<pre><dfn><counter-style></dfn> = <identifier> | <symbols-function></pre>
<p>where the <identifier> must be the name of a valid custom counter style defined with the ''@counter-style'' rule.</p>
<!-- ====================================================================== -->
<h2 id='list-style-position-property'>
Marker Position: The 'list-style-position' property</h2>
<table class="propdef">
<tr>
<th>Name:
<td><dfn>list-style-position</dfn>
<tr>
<th>Value:
<td>inside | outside
<tr>
<th>Initial:
<td>outside
<tr>
<th>Applies To:
<td><i title="list item">list items</i>
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed Value:
<td>specified value
</table>
<p>This property specifies the position of the <code class=css>::marker</code> pseudo-element's box
in the <i>list item</i>. Values have the following meanings:</p>
<dl>
<dt><dfn>inside</dfn></dt>
<dd>The <code class=css>::marker</code> pseudo-element is a 'display:inline' element placed immediately before the ''::before'' pseudo-element in the <i>list item</i>'s principle box, after which the element's content flows. Note that if there is no inline content, this will create a line box, just as content in an inline ''::before'' pseudo-element would. Also note that all the properties that apply to inline elements apply to the <code class=css>::marker</code> pseudo-element in this state, and this <code class=css>::marker</code> box participates in the inline box model in the normal manner.</dd>
<dt><dfn>outside</dfn></dt>
<dd>As ''inside'', plus the 'position' property on the <code class=css>::marker</code> pseudo-element must computer to ''marker''. The section on the new 'marker' value for 'position' explains the consequences of this. Additionally, the base directionality of the <code class=css>::marker</code> pseudo-element (used as an input to the bidi resolution algorithm) must be taken from the marker's <i>marker positioning reference element</i>.</dd>
</dl>
<p>Note that a marker is only generated if the computed value of the 'content'
property for the element's <code class=css>::marker</code> pseudo-element is not ''none''.</p>
<p class='issue'>Should I make this always compute to ''inside'' when the list item is ''display:inline-list-item''? See the thread at <a href="http://lists.w3.org/Archives/Public/www-style/2011Jun/0232.html">http://lists.w3.org/Archives/Public/www-style/2011Jun/0232.html</a>.</p>
<div class=example>
<p>For example:
<pre>
<style>
ul.compact { list-style: inside; }
ul { list-style: outside; }
</style>
<ul class=compact>
<li>first "inside" list item comes first</li>
<li>second "inside" list item comes first</li>
</ul>
<hr>
<ul>
<li>first "outside" list item comes first</li>
<li>second "outside" list item comes first</li>
</ul></pre>
<p>The above example may be formatted as:</p>
<pre>
* first "inside" list
item comes first
* second "inside" list
item comes second
========================
* first "outside" list
item comes first
* second "outside" list
item comes second</pre>
</div>
<!-- ====================================================================== -->
<h2 id='list-style-property'>
The 'list-style' shorthand property</h2>
<table class="propdef">
<tr>
<th>Name:
<td><dfn>list-style</dfn>
<tr>
<th>Value:
<td><'list-style-type'> || <'list-style-position'> || <'list-style-image'>
<tr>
<th>Initial:
<td>see individual properties
<tr>
<th>Applies To:
<td><i title="list item">list items</i>
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed Value:
<td>see individual properties
</table>
<p>The 'list-style' property is a shorthand notation for setting the
three properties 'list-style-type', 'list-style-image', and 'list-style-position'
at the same place in the style sheet.</p>
<div class="example">
<p>For example:</p>
<pre>
UL { list-style: upper-roman inside } /* Any UL */
UL UL { list-style: circle outside } /* Any UL child of a UL */
</pre>
</div>
<p>Using a value of ''none'' in the shorthand is potentially ambiguous, as ''none'' is a valid value for both 'list-style-image' and 'list-style-type'. To resolve this ambiguity, a value of ''none'' in the shorthand must be applied to whichever of the two properties aren't otherwise set by the shorthand.</p>
<div class='example'>
<pre>
list-style: none disc;
/* Sets the image to "none" and the type to "disc". */
list-style: none url(bullet.png);
/* Sets the image to "url(bullet.png)" and the type to "none". */
list-style: none;
/* Sets both image and type to "none". */
list-style: none disc url(bullet.png);
/* Syntax error */</pre>
</div>
<p>Although authors may specify 'list-style' information directly on list item elements (e.g., LI in HTML), they should do so with care. Consider the following rules:</p>
<div class=example>
<pre>
ol.alpha li { list-style: lower-alpha; }
ul li { list-style: disc; }
/* These won't work as expected. If you nest a <ul>
into an <ol class=alpha>, the first rule's specificity
will make the <ul>'s list items use the lower-alpha style. */
ol.alpha > li { list-style: lower-alpha; }
ul > li { list-style: disc; }
/* These work as intended. */
ol.alpha { list-style: lower-alpha; }
ul { list-style: disc; }
/* So do these, since inheritance will transfer the
'list-style' value to the list items. */</pre>
</div>
<!-- ====================================================================== -->
<h2 id='marker-pseudo-element'>
Markers: The <code class=css>::marker</code> pseudo-element</h2>
<p>Markers are created by setting an element's 'display' property to
''list-item'' or ''inline-list-item''. The <code class=css>::marker</code> pseudo-element is only created if
the computed value of the 'content' property for the pseudo-element is not
''none''.</p>
<p>Just like other generated content, markers generate a box when they're created, which can be styled with the full range of properties and values. Markers are placed at the beginning of their superior parent's content, before the ::before pseudo-element (if it exists). <code class=css>::marker</code> pseudo-elements are inline by default, though certain values for 'list-style-position' on the list item can make the marker box positioned, which can have an effect on the computed value of display.</p>
<div class="example">
<p>In the following example, the content is centered within a marker
box of a fixed width. This document:</p>
<pre>
<style>
li::marker {
content: "(" counter(counter) ")";
width: 6em;
text-align: center;
}
li {
display: list-item;
counter-increment: counter;
}
</style>
<ol>
<li>This is the first item.</li>
<li>This is the second item.</li>
<li>This is the third item.</li>
</ol></pre>
<p>should render something like this: </p>
<pre>
(1) This is the
first item.
(2) This is the
second item.
(3) This is the
third item.</pre>
</div>
<div class="example">
<p>In this example, markers are used to number paragraphs that are designated as "notes":</p>
<pre>
<style>
p { margin-left: 12 em; }
p.note::marker {
content: "Note " counter(note-counter) ":";
text-align: left;
width: 10em;
}
p.note {
display: list-item;
counter-increment: note-counter;
}
</style>
<p>This is the first paragraph in this document.</p>
<p class="note">This is a very short document.</p>
<p>This is the end.</p>
</pre>
<p>It should render something like this:</p>
<pre>
This is the first paragraph
in this document.
Note 1: This is a very short
document.
This is the end.</pre>
</div>
<div class="example">
<p>By using the <code class=css>::marker</code> pseudo-element, a list's markers can be positioned much more flexibly, and even be styled independently from the text of the list item itself:</p>
<pre>
<style>
p { margin-left: 8em } /* Make space for counters */
li { list-style-type: lower-roman; }
li::marker { margin: 0 3em 0 0; color: blue; }
</style>
<p>This is a long preceding paragraph ...</p>
<ol>
<li>This is the first item.</li>
<li>This is the second item.</li>
<li>This is the third item.</li>
</ol>
<p>This is a long following paragraph ...</p></pre>
<p>The preceding document should render something like this: </p>
<pre>
This is a long preceding
paragraph ...
<span style=color:blue>i.</span> This is the first item.
<span style=color:blue>ii.</span> This is the second item.
<span style=color:blue>iii.</span> This is the third item.
This is a long following
paragraph ...</pre>
<p>Previously the only way to style a marker was through inheritance; one had to put the desired marker styling on the list item, and then revert that on a wrapper element around the list item's actual contents. Non-inherited properties like 'margin' couldn't be adjusted at all on the marker.</p>
</div>
<!-- ====================================================================== -->
<h3 id='content-property'>
Generating the computed value of the 'content' property</h3>
<p>If a <code class=css>::marker</code> pseudo-element has its 'content' property set to ''normal'',
the computed value of the marker's 'content' property must be determined
according to the following algorithm:</p>
<ol>
<li>If the computed value of 'list-style-image' is a valid <image>, then
the computed value of the 'content' property is that image.</li>
<li>Otherwise, if the computed value of 'list-style-type' is a <string>, then
the computed value of the 'content' property is that string.</li>
<li>Otherwise, if the computed value of 'list-style-type' is a valid <i><counter-style></i>, then the computed value of the 'content' property is <code><counter-prefix> counter(list-item, <counter-style>) <counter-suffix></code>, where <i><counter-prefix></i> and <i><counter-suffix></i> are the values of the <i title='counter-prefix'>prefix</i> and <i title='counter-suffix'>suffix</i> descriptors for the counter style.</li>
<li>Otherwise the computed value is ''none''.</li>
</ol>
<div class="example">
<p>Given the following style sheet:</p>
<pre>
li { display: list-item; list-style-type: decimal /* initial value */; }
li<code class=css>::marker</code> { content: normal /* initial value */; }</pre>
<p>And the following document fragment:</p>
<pre><li>List Item</li></pre>
<p>The computed value of the 'content' property on the <code class=css>::marker</code> pseudo-element of the list item element is:</p>
<pre>counter(list-item, decimal) "."</pre>
</div>
<!-- ===================================================================== -->
<h2 id='positioning-markers'>
Positioning Markers</h2>
<p>This section introduces a new positioning scheme, designed to model the
way in which "outside" list markers were traditionally positioned in CSS 2.1.
Outside list markers now have their positioning defined in terms of this new
value.</p>
<p>The new positioning scheme defined in this section can be used on all
elements, not just <code class=css>::marker</code> pseudo-elements. In some situations, such as
legal proceedings or official minutes, the precise form that the list marker
takes is a vital part of the content. It's not acceptable for the marker to
change (from a custom-defined marker to a default bullet or alpha marker)
just because the UA is not rendering CSS, or a server error is temporarily
preventing the CSS file from being loaded, as the precise form of the marker
is used to officially refer to that segment. The only way to guarantee that
the marker will be rendered correctly, regardless of whether CSS is applied,
is to specify the marker outside of CSS, directly in the document's markup.
However, the page author may still want to style the marker in many of the
ways that are available to them when using ordinary CSS-generated markers.
To accomodate this, the new positioning scheme can be used to position the
marker-in-content as if it were an ordinary CSS-generated marker.</p>
<h3 id='position-marker'>
The ''marker'' value for 'position'</h3>
<table class="propdef">
<tr>
<th>Property:
<td>'position'
<tr>
<th>New Value:
<td>''marker''
<tr>
<th>Initial:
<td>same as CSS2.1
<tr>
<th>Applies to:
<td>same as CSS2.1
<tr>
<th>Inherited:
<td>same as CSS2.1
<tr>
<th>Percentages:
<td>same as CSS2.1
<tr>
<th>Media:
<td>same as CSS2.1
<tr>
<th>Computed value:
<td>see prose, otherwise same as CSS2.1
</table>
<p>The ''marker'' value for 'position' depends on the element it is set on having a list item ancestor. If the specified value of 'position' is ''marker'' and the element does not have a list item ancestor, 'position' must compute to 'relative' on the element. An element with <code class=css>position:marker</code> counts as <a href="http://www.w3.org/TR/CSS21/visuren.html#absolutely-positioned">absolutely positioned</a>.</p>
<p>To calculate the marker's position, we must first define a few terms:</p>
<dl>
<dt><dfn title="ancestor list item|ancestor list item's">ancestor list item</dfn></dt>
<dd>The <i>ancestor list item</i> is the marker's nearest list item ancestor element.</dd>
<dt><dfn>marker positioning reference element</dfn></dt>
<dd>
<p>If the <i>ancestor list item</i> has ''marker-attachment:list-item'', the <i>marker positioning reference element</i> is the <i>ancestor list item</i>.</p>
<p>Otherwise, if the <i>ancestor list item</i> has ''marker-attachment:list-container'' and has a parent element, the <i>marker positioning reference element</i> is the <i>ancestor list item's</i> parent.</p>
<p>Otherwise, the <i>marker positioning reference element</i> is the <i>ancestor list item</i>.</p>
</dd>
<dt><dfn>list item positioning edge</dfn></dt>
<dd>The border edge of the <i>ancestor list item</i> corresponding to the "start" or "before" edge of the <i>marker positioning reference element</i>, whichever is in the <i>ancestor list item's</i> inline axis.</dd>
<dt><dfn>marker positioning edge</dfn></dt>
<dd>The opposing edge relative to the <i>list item positioning edge</i> on the marker's margin box. For example, if the <i>list item positioning edge ended up being the left border edge of the <i>ancestor list item</i>, the <i>marker positioning edge</i> would be the right margin edge of the marker.</dd>
</dl>
<p>The marker's position in the <i>ancestor list item's</i> block axis is calculated according to the <a href="http://www.w3.org/TR/CSS21/visuren.html#normal-flow">normal flow</a>. <span class='note'>In the Positioned Layout Module this will be defined more precisely in terms of placeholders.</span></p>
<p>The marker's position in the <i>ancestor list item's</i> inline axis must be set such that the <i>marker positioning edge</i> is flush with the <i>list item positioning edge</i>.</p>
<p class='note'>The purpose of this somewhat convoluted definition is to position the marker flush against its list item, and then when "marker-attachment:list-container", keep all the markers for a given list on the same side of their list items even in mixed-direction text, so that authors can specify padding on only one side and still ensure their markers are visible. And on top of all that, do something sane in the face of potentially differing writing-modes on the marker, list item, and container.</p>
<p>All elements or pseudo-elements with <code class=css>"position:marker"</code> that share a common <i>ancestor list item</i> are known as <dfn title='associated-marker'>markers associated with that list item</dfn>.</p>
<p>The 'top', 'right', 'bottom', and 'left' properties specify offsets relative to the top, right, bottom, and left edges (respectively) of the element itself, similar to how relative positioning works.</p>
<div class='example'>
<p>''position:marker'' can be used when the precise list marker is important for the content, not a stylistic choice, but the normal <em>appearance</em> of lists is still desired. For example, this trimmed snippet of the US Code of Laws may be marked up as the following in HTML:</p>
<pre>
<style>
ol { list-style: none; }
.marker { position: marker; }
</style>
<ol>
<li>
<span class='marker'>(a)</span> Definitions.— For purposes of this section—
<ol>
<li><span class='marker'>(1)</span> the term “agency” means agency as...</li>
<li><span class='marker'>(2)</span> the term “individual” means a citizen...</li>
</ol>
</li>
<li>
<span class='marker'>(b)</span> Conditions of Disclosure.— No agency shall disclose...
<ol>
<li><span class='marker'>(1)</span> to those officers and employees of the agency which...</li>
<li><span class='marker'>(2)</span> required under section 552 of this title;</li>
</ol>
</li>
</ol></pre>
<p>The preceding document should render something like this:</p>
<pre>
(a) Definitions.— For purposes of this section—
(1) the term “agency” means agency as...
(2) the term “individual” means a citizen...
(b) Conditions of Disclosure.— No agency shall disclose...
(1) to those officers and employees of the agency which...
(2) required under section 552 of this title;</pre>
<p>Importantly, it will <strong>always</strong> be presented something like that, with those exact list markers, even if the stylesheet is unavailable, so other documents can refer to those list markers and be confident that the reference will always be resolvable.</p>
</div>
<h3 id='marker-attachment'>
The 'marker-attachment' property</h3>
<p>By default, elements or <code class=css>::marker</code> pseudo-elements with ''position:marker'' position themselves according to their list item's directionality. However, if the list item is grouped with several other list items which may have different directionality (for example, multiple <li>s with different "dir" attributes in an <ol> in HTML), it is sometimes more useful to have all the markers line up on one side, so the author can specify a single "gutter" on that side and be assured that all the markers will lie in that gutter and be visible. The 'marker-attachment' property defined in this section allows an author to control this, switching list items to positioning their markers based off the list container's directionality instead.</p>
<table class="propdef">
<tr>
<th>Property:
<td><dfn>marker-attachment</dfn>
<tr>
<th>Value:
<td>list-item | list-container
<tr>
<th>Initial:
<td>list-item
<tr>
<th>Applies to:
<td><i title="list item">list items</i>
<tr>
<th>Inherited:
<td>yes
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>visual
<tr>
<th>Computed Value:
<td>specified value
</table>
<p>When a list item has ''marker-attachment:list-item'', any <i title='associated-marker'>markers associated with the list item</i> base their positioning off of the directionality of the list item. When a list item has ''marker-attachment:list-container'', the <i title='associated-marker'>associated markers</i> instead base their positioning off of the directionality of the list item's parent element. The normative meaning of this is specified in the section defining <a href="#position-marker">position:marker</a>.</p>
<div class='example'>
<p>Here is a visual rendering of the effect that 'marker-attachment' can have on a list. Both of the following renderings are generated from the following HTML, with the only difference being the value of 'marker-attachment' on the list:</p>
<pre>
<ul>
<li>english one
<li dir=rtl>OWT WERBEH
<li>english three
<li dir=rtl>RUOF WERBEH
</ul></pre>
<table class=data style="width: 35em;">
<thead>
<tr>
<th>list-item
<th>list-container
<tbody>
<tr>
<td style="border-right: thin solid">
<ul>
<li>english one
<li dir=rtl>OWT WERBEH
<li>english three
<li dir=rtl>RUOF WERBEH
</ul>
<td>
<ul>
<li>english one
<li>OWT WERBEH
<li>english three
<li>RUOF WERBEH
</ul>
</table>
</div>
<!-- ===================================================================== -->
<h2 id='counter'>
Automatic Counters and Numbering: the 'counter-increment', 'counter-set' and 'counter-reset' properties</h2>
<p>Automatic numbering in CSS2 is controlled with three properties: 'counter-increment', 'counter-set' and 'counter-reset'. The <dfn title="list counter">counters</dfn> defined by these properties are used with the ''counter()'' and ''counters()'' functions.
<table class="propdef">
<tr>
<th>Name:
<td><dfn>counter-increment</dfn>
<tr>
<th>Value:
<td>[ <identifier> <integer>? ]+ | none
<tr>
<th>Initial:
<td>none
<tr>
<th>Applies To:
<td>all elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>all
<tr>
<th>Computed value:
<td>specified value
</table>
<table class="propdef">
<tr>
<th>Name:
<td><dfn>counter-set</dfn>
<tr>
<th>Value:
<td>[ <identifier> <integer>? ]+ | none
<tr>
<th>Initial:
<td>none
<tr>
<th>Applies To:
<td>all elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>all
<tr>
<th>Computed value:
<td>specified value
</table>
<table class="propdef">
<tr>
<th>Name:
<td><dfn>counter-reset</dfn>
<tr>
<th>Value:
<td>[ <identifier> <integer>? ]+ | none
<tr>
<th>Initial:
<td>none
<tr>
<th>Applies To:
<td>all elements
<tr>
<th>Inherited:
<td>no
<tr>
<th>Percentages:
<td>N/A
<tr>
<th>Media:
<td>all
<tr>
<th>Computed value:
<td>specified value
</table>
<p>The 'counter-increment' property accepts one or more names of counters (identifiers), each one optionally followed by an integer. The integer indicates by how much the counter is incremented for the element it's set on. The default increment is ''1''.</p>
<p>The 'counter-set' and 'counter-reset' properties also contains a list of one or more names of counters, each one optionally followed by an integer. The integer gives the value that the counter is set to on the element it's set on. The default is ''0''.</p>
<p>On all of these properties, a value of 'none' means that no counters are incremented, set, or reset, respectively. Counter names must not be 'initial', 'inherit', or 'none'; using one of these keywords as a counter name makes the property invalid.</p>
<p>'counter-reset' always establishes a new <i>counter scope</i> on the element it's set on. 'counter-increment' and 'counter-set' sometimes establish a new <i>counter scope</i> on the element they're set on.</p>
<div class="example">
<p>This example shows a way to number chapters and sections with "Chapter 1", "1.1", "1.2", etc.
<pre>
H1:before {
content: "Chapter " counter(chapter) ". ";
counter-increment: chapter; /* Add 1 to chapter */
counter-reset: section; /* Set section to 0 */
}
H2:before {
content: counter(chapter) "." counter(section) " ";
counter-increment: section;
}</pre>
</div>
<p>Resetting a counter is done <em>before</em> setting a counter, which is done <em>before</em> incrementing a counter, which is done <em>before</em> using a counter (for example, in the 'content' property).</p>
<div class='note'>
<p>The counter properties follow the cascading rules as normal. Thus, due to cascading, the following style sheet:</p>
<div class='example'>
<pre>
H1 { counter-reset: section -1 }
H1 { counter-reset: imagenum 99 }</pre>
</div>
<p>will only reset 'imagenum'. To reset both counters, they have to be specified together:</p>
<div class='example'>
<pre>H1 { counter-reset: section -1 imagenum 99 }</pre>
</div>
<p>The same principles apply to the 'counter-set' and 'counter-increment' properties.</p>
</div>
<h3 id="nested-counters">
Nested counters and scope</h3>
<p>Counters are "self-nesting", in the sense that resetting a counter in a child element automatically creates a new instance of the counter. This is important for situations like lists in HTML, where lists can be nested inside lists to arbitrary depth. It would be impossible to define uniquely named counters for each level.
<div class="example">
<p>Thus, the following suffices to number nested list items. The result is very similar to that of setting 'display:list-item' and 'list-style: inside' on the LI element:
<pre>
OL { counter-reset: item }
LI { display: block }
LI:before { content: counter(item) ". "; counter-increment: item }</pre>
</div>
<p>The self-nesting is based on the principle that every element or pseudo-element that has a 'counter-reset' for a counter X, creates a fresh counter X, the <dfn id="counter-scope" title="scope|counter scope">scope</dfn> of which is the element or pseudo-element, its following siblings up to but not including the first one that resets the same counter, and all the descendants of those elements.</p>
<p>Additionally, if an element has a 'counter-set' or 'counter-increment' for a counter that is not in scope for the element, it establishes a scope for that counter identically to if 'counter-reset' were used on the element to reset the counter to ''0''.
<p>In the example above, an OL will create a counter, and all children of the OL will refer to that counter.
<div class="html-example">
<p>If we denote by item[<var>n</var>] the <var>n</var><sup>th</sup> instance of the "item" counter, and by "(" and ")"the beginning and end of a scope, then the following HTML fragment will use the indicated counters. (We assume the style sheet as given in the example above).
<pre>
<OL> <!-- (set item[0] to 0 -->
<LI>item <!-- increment item[0] to 1 -->
<LI>item <!-- increment item[0] to 2 -->
<OL> <!-- (set item[1] to 0 -->
<LI>item <!-- increment item[1] to 1 -->
<LI>item <!-- increment item[1] to 2 -->
<LI>item <!-- increment item[1] to 3 -->
<OL> <!-- (set item[2] to 0 -->
<LI>item <!-- increment item[2] to 1 -->
</OL> <!-- ) -->
<OL> <!-- (set item[3] to 0 -->
<LI> <!-- increment item[3] to 1 -->
</OL> <!-- ) -->
<LI>item <!-- increment item[0] to 3 -->
<LI>item <!-- increment item[0] to 4 -->
</OL> <!-- ) -->
<OL> <!-- (set item[4] to 0 -->
<LI>item <!-- increment item[4] to 1 -->
<LI>item <!-- increment item[4] to 2 -->
</OL> <!-- ) --></pre>
</div>
<p>As explained in a later section, the ''counter()'' function generates a string based off of the innermost scope of the named counter, while the ''counters()'' function generates a string based on the values of <em>all</em> the in-scope counters with a given name.</p>
<div class="example"><p>
<p>The following style sheet numbers nested list items
as "1", "1.1", "1.1.1", etc.
<pre>
OL { counter-reset: item }
LI { display: block }
LI:before { content: counters(item, "."); counter-increment: item }</pre>
</div>