csswg-drafts/css2/cover.src at 493f524bd29c2664c67d2d9eaed88f9807d7ae30 · w3c/csswg-drafts · GitHub

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">

<html lang="en">

<title>Cascading Style Sheets Level 2 Revision 1 (CSS&nbsp;2.1) Specification</title>

<body>
<div class="head">
  <p><a href="http://www.w3.org/"><img alt="W3C" height="48"
    src="http://www.w3.org/Icons/w3c_home" width="72"></a>

  <h1 id="title">Cascading Style Sheets Level 2 Revision 1 (CSS&nbsp;2.1) Specification</h1>
  <h2 id="W3C-doctype">W3C _THE_STATUS_ _THE_DATE_</h2>

  <dl>
  <dt>This version:
  <dd><a href="_THIS_VERSION_">
               _THIS_VERSION_</a>
  <dt>Latest version:
  <dd><a href="_THE_LATEST_VERSION_">
               _THE_LATEST_VERSION_</a>
  <dt>Previous versions:
  <dd><a href="_THE_PREVIOUS_VERSION_">
               _THE_PREVIOUS_VERSION_</a>
  <dd><a href="http://www.w3.org/TR/1998/REC-CSS2-19980512/">
               http://www.w3.org/TR/1998/REC-CSS2-19980512/</a>
  <dt>Editors:
  <dd class="vcard"><a class="url fn" lang=nl href="http://www.w3.org/People/Bos/">
               Bert Bos</a>
            &lt;<span class="email">bert&nbsp;@w3.org</span>&gt;</dd>
  <dd class="vcard"><a class="url fn" lang=tr href="http://tantek.com/">
               Tantek &Ccedil;elik</a>
            &lt;<span class="email">tantek&nbsp;@cs.stanford.edu</span>&gt;</dd>
  <dd class="vcard"><a class="url fn" lang=en href="http://ian.hixie.ch/">
               Ian Hickson</a>
               &lt;<span class="email">ian&nbsp;@hixie.ch</span>&gt;</dd>
  <dd class="vcard"><a class="url fn n" lang=no href="http://people.opera.com/howcome/">
<span class="given-name">H&aring;kon</span> <span class="additional-name">Wium</span> <span class="family-name">Lie</span></a>
               &lt;<span class="email">howcome&nbsp;@opera.com</span>&gt;</dd>
  </dl>

  <p>Please refer to the <a
  href="_THE_UPDATE_DIR_/_THE_ID_-errata.html"><strong>
  errata</strong></a> for this document.

  <p>This document is also available in these non-normative formats:
  <a href="css2.txt">plain text</a>,
  <a href="css2.tgz">gzip'ed tar file</a>,
  <a href="css2.zip">zip file</a>,
  <a href="css2.ps.gz">gzip'ed PostScript</a>,
  <a href="css2.pdf">PDF</a>.
  See also <a
  href="_THE_UPDATE_DIR_/translations.html"><strong>
  translations</strong></a>.

  <p class="copyright"><a
  href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">
  Copyright</a> &copy; 2007 <a href="http://www.w3.org/"><acronym
  title="World Wide Web Consortium">W3C</acronym></a><sup>&reg;</sup>
  (<a href="http://www.csail.mit.edu/"><acronym title="Massachusetts
  Institute of Technology">MIT</acronym></a>, <a
  href="http://www.ercim.org/"><acronym title="European Research
  Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a
  href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a
  href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">
  liability</a>, <a
  href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">
  trademark</a> and <a
  href="http://www.w3.org/Consortium/Legal/copyright-documents">
  document use</a> rules apply.

  <hr title="Separator from Header">
</div>

<h2 id=abstract>Abstract</h2>

<p>This specification defines Cascading Style Sheets, level&nbsp;2
revision&nbsp;1 (CSS&nbsp;2.1). CSS&nbsp;2.1 is a style sheet language
that allows
authors and users to attach style (e.g., fonts and spacing) to
structured documents (e.g., HTML documents and XML
applications). By separating the presentation style of documents from
the content of documents, CSS&nbsp;2.1 simplifies Web authoring and
site maintenance.

<P>CSS&nbsp;2.1 builds on CSS2 [[-CSS2]] which builds on CSS1 [[-CSS1]].
It supports media-specific style sheets so that authors may tailor the
presentation of their documents to visual browsers, aural devices,
printers, braille devices, handheld devices, etc. It also supports
content positioning, table layout, features for internationalization
and some properties related to user interface.

<p>CSS&nbsp;2.1 corrects a few errors in CSS2 (the most important
being a new definition of the height/width of absolutely positioned
elements, more influence for HTML's "style" attribute and a new
calculation of the 'clip' property), and adds a few highly requested
features which have already been widely implemented.
But most of all CSS&nbsp;2.1
represents a "snapshot" of CSS usage: it consists of all CSS features
that are implemented interoperably at the date of publication of the Recommendation.

<p>CSS&nbsp;2.1 is derived from and is intended to replace CSS2. Some
parts of CSS2 are unchanged in CSS&nbsp;2.1, some parts have been
altered, and some parts removed. The removed portions may be used in a
future CSS3 specification. Future specs should refer to CSS&nbsp;2.1
(unless they need features from CSS2 which have been dropped in
CSS&nbsp;2.1, and then they should only reference CSS2 for those
features, or preferably reference such feature(s) in the respective
CSS3 Module that includes those feature(s)).

<h2 id=status>Status of this document</h2>

<p><em>This section describes the status of this document at the time
of its publication. Other documents may supersede this document. A
list of current W3C publications and the latest revision of this
technical report can be found in the <a
href="http://www.w3.org/TR/">W3C technical reports index at
http://www.w3.org/TR/</a>.</em>

<p>This is a W3C Candidate Recommendation, which means the
specification has been widely reviewed and W3C recommends that it be
implemented. It will remain Candidate Recommendation
<a href="#crec">at least until 20 December 2007.</a> A test suite and
a report on implementations will be provided before the document becomes
a Proposed Recommendation.</p>

<p>Publication as a Candidate Recommendation does not imply endorsement
by the W3C Membership. This is a draft document and may be updated,
replaced or obsoleted by other documents at any time. It is inappropriate
to cite this document as other than work in progress.</p>

<p>The (<a
href="http://lists.w3.org/Archives/Public/www-style/">archived</a>)
public mailing list <a
href="mailto:www-style@w3.org">www-style@w3.org</a> (see <a
href="http://www.w3.org/Mail/Request">instructions</a>) is preferred
for discussion of this specification. When sending e-mail, please put
the text &#8220;[CSS21]&#8221; in the subject, preferably like
this: &#8220;[CSS21] <em>&hellip;summary of
comment&hellip;</em>&#8221;</p>

<p>This document incorporates <a
href="/Style/css2-updates/CR-CSS21-20070719-errata.html"> errata</a>
resulting from implementation experience since the previous
publication. Some of the corrections remove ambiguities or change the
behavior in edge cases, and therefore it is expected that another
Working Draft will (briefly) precede the Proposed Recommendation, in
order to invite more review.

<p>This document was produced by the <a
href="/Style/CSS/members">CSS Working Group</a> (part
of the <a href="/Style/">Style Activity</a>).

<p>This document was produced by a group operating under
the <a href="/Consortium/Patent-Policy-20040205/">5
February 2004 W3C Patent Policy</a>. W3C maintains
a <a rel="disclosure" href="/2004/01/pp-impl/32061/status">public list of any
patent disclosures</a> made in connection with the deliverables of the
group; that page also includes instructions for disclosing a patent.
An individual who has actual knowledge of a patent which the
individual believes
contains <a
href="/Consortium/Patent-Policy-20040205/#def-essential">Essential
Claim(s)</a> must disclose the information in accordance
with <a
href="/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of
the W3C Patent Policy</a>.</p>


<h3 class="no-num" id="crec">Candidate Recommendation Exit Criteria</h3>

<p>For this specification to exit the CR stage, the following
conditions must be met:</p>
 <ol>
  <li>
   <p>There must be at least two interoperable implementations
   for every feature. For the purposes of this criterion,
   we define the following terms:</p>
   <dl>
    <dt>feature</dt>
    <dd>
     <p>
      A section or subsection of the specification.
     </p>
    </dd>
    <dt>interoperable</dt>
    <dd>
     <p>passing the respective test cases in the test suite, or,
     if the implementation is not a web browser, equivalent tests.
     Every relevant test in the test suite should have an equivalent
     test created if such a UA is to be used to claim interoperability.
     In addition if such a UA is to be used to claim interoperability,
     then there must one or more additional UAs which can also pass
     those equivalent tests in the same way for the purpose of
     interoperability. The equivalent tests must be made publicly
     available for the purposes of peer review.</p>
    </dd>

9721
    <dt>implementation</dt>
    <dd>
     <p>a user agent which:</p>
     <ol>
      <li>implements the feature.</li>
      <li>is available (i.e. publicly downloadable or available
      through some other public point of sale mechanism). This is the
      "show me" requirement.</li>
      <li>is shipping (i.e. development, private or unofficial
      versions are insufficient).</li>
      <li>is not experimental (i.e. is intended for a wide audience
      and could be used on a daily basis).</li>
     </ol>
    </dd>
   </dl>
  </li>
  <li><p>A minimum of six months of the CR period must have elapsed.
  This is to ensure that enough time is given for any remaining major
  errors to be caught.</p></li>
  <li><p>The CR period will be extended if implementations are slow to
  appear.</p></li>
  <li><p>Features that were not in CSS1 will be dropped (thus reducing the
   list of "all" features mentioned above) if two or more
   interoperable implementations of those features are not found by
   the end of the CR period.</p></li>
  <li><p>Features will also be dropped if sufficient and adequate
  tests (by judgment of the working group) have not been produced for
  those features by the end of the CR period.</p></li>
 </ol>

<h3 id=at-risk>Features at risk</h3>

<p>The working group has identified the following features as being
currently poorly implemented by UAs. They are therefore most at risk
of being removed from CSS&nbsp;2.1 when exiting CR. (Any changes of this
nature will still result in the specification being returned to last
call.) Implementors are urged to implement these features, or correct
bugs in their implementations, if they wish to see these features remain
in this specification.</p>
<dl>
 <dt>New 'list-style-type' values</dt>
 <dd>
  <ul>
   <li>'armenian'</li>
   <li>'georgian'</li>
   <li>'lower-greek'</li>
  </ul>
  <p>Implementors are advised to look at CSS3 Lists instead, where these and
  many other new values not found in CSS1 are defined in detail.
  [[-CSS3LIST]]</p>
 <dt>Support for multiple ID attributes for the ID selector
 <dd>
  <p>Because implementations are not expected to support multiple IDs
  per element soon, this feature may be made informative. The W3C
  Selectors specification will continue to have this feature
  normatively. (<a href="selector.html#id-selectors">Section
  5.9.</a>)
 </dd>
 <dt>Automatic table layout algorithm
 <dd>
  <p>The input to the suggested (non-normative) automatic layout
  algorithm for tables is restricted to (1) the containing block width
  and (2) the content and properties of the table and its
  children. This restriction may be lifted.
 <dt>Quotes
 <dd>
 <p>The <span class="propinst-quotes">'quotes'</span> property and the
 'open-quote', 'close-quote', 'no-open-quote' and 'no-close-quote'
 keywords may be dropped.
 <dt>BODY element in XHTML
 <dd>
 <p>The effect of <a href="visufx.html#overflow">'overflow'</a> and <a
 href="colors.html#background">'background'</a> is different on BODY elements
 in HTML than on other elements. It may be that the exceptional
 handling of BODY in HTML is extended to BODY in XHTML1.
</dl>

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