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<!doctype html><html lang="en">
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<title>CSS Mobile Profile 2.0</title>
<meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
<meta content="abandoned" name="csswg-work-status">
<meta content="ED" name="w3c-status">
<meta content=" <p>This specification defines in general a subset of <acronym title="Cascading Style Sheets">CSS</acronym> 2.1 [[!CSS21]] that is to be considered a baseline for interoperability between implementations of <acronym title="Cascading Style Sheets">CSS</acronym> on constrained devices (e.g. mobile phones). Its intent is <em>not</em> to produce a profile of <acronym title="Cascading Style Sheets">CSS</acronym> incompatible with the complete specification, but rather to ensure that implementations that due to platform limitations cannot support the entire specification implement a common subset that is interoperable not only amongst constrained implementations but also with complete ones. Additionally, this specification aligns itself as much as possible with the <acronym title="Open Mobile Alliance">OMA</acronym> Wireless <acronym title="Cascading Style Sheets">CSS</acronym> 1.1 [[WCSS11]] specification. At the same time, <acronym title="Open Mobile Alliance">OMA</acronym> is doing alignment work in <acronym title="Open Mobile Alliance">OMA</acronym> Wireless <acronym title="Cascading Style Sheets">CSS</acronym> 1.2 [[WCSS12]]. It is aimed at aligning the mandatory compliance items between <acronym title="Cascading Style Sheets">CSS</acronym> Mobile Profile 2.0 and <acronym title="Open Mobile Alliance">OMA</acronym> Wireless <acronym title="Cascading Style Sheets">CSS</acronym> 1.2 [[WCSS12]].</p> <p class=mtb><strong>This profile is obsolete. Please see the latest <a href="https://www.w3.org/TR/CSS/" >CSS Snapshot</a> for the specifications that make up CSS.</strong></p>" name="abstract">
<link href="../default.css" rel="stylesheet" type="text/css">
<link href="../csslogo.ico" rel="shortcut icon" type="image/x-icon">
<style>
body {
background: url("https://www.w3.org/StyleSheets/TR/logo-ED") top left no-repeat;
};
</style>
<meta content="Bikeshed version f2fabcb59230e0dd4e9ee94c1d560098d994398a" name="generator">
<meta charset="utf-8">
<style type="text/css">
table.features th {
background: #00589f;
color: #fff;
text-align: left;
padding: 0.2em 0.2em 0.2em 0.5em;
}
table.features td {
vertical-align: top;
border: 1px solid #ccc;
padding: 0.3em 0.3em 0.3em 0.7em;
}
tr.optional { background: aqua; }
em.rfc2119 {
text-transform: lowercase;
font-variant: small-caps;
font-style: normal
}
</style>
<style>/* style-md-lists */
/* This is a weird hack for me not yet following the commonmark spec
regarding paragraph and lists. */
[data-md] > :first-child {
margin-top: 0;
}
[data-md] > :last-child {
margin-bottom: 0;
}</style>
<style>/* style-counters */
body {
counter-reset: example figure issue;
}
.issue {
counter-increment: issue;
}
.issue:not(.no-marker)::before {
content: "Issue " counter(issue);
}
.example {
counter-increment: example;
}
.example:not(.no-marker)::before {
content: "Example " counter(example);
}
.invalid.example:not(.no-marker)::before,
.illegal.example:not(.no-marker)::before {
content: "Invalid Example" counter(example);
}
figcaption {
counter-increment: figure;
}
figcaption:not(.no-marker)::before {
content: "Figure " counter(figure) " ";
}</style>
<style>/* style-selflinks */
.heading, .issue, .note, .example, li, dt {
position: relative;
}
a.self-link {
position: absolute;
top: 0;
left: calc(-1 * (3.5rem - 26px));
width: calc(3.5rem - 26px);
height: 2em;
text-align: center;
border: none;
transition: opacity .2s;
opacity: .5;
}
a.self-link:hover {
opacity: 1;
}
.heading > a.self-link {
font-size: 83%;
}
li > a.self-link {
left: calc(-1 * (3.5rem - 26px) - 2em);
}
dfn > a.self-link {
top: auto;
left: auto;
opacity: 0;
width: 1.5em;
height: 1.5em;
background: gray;
color: white;
font-style: normal;
transition: opacity .2s, background-color .2s, color .2s;
}
dfn:hover > a.self-link {
opacity: 1;
}
dfn > a.self-link:hover {
color: black;
}
a.self-link::before { content: "¶"; }
.heading > a.self-link::before { content: "§"; }
dfn > a.self-link::before { content: "#"; }</style>
<style>/* style-autolinks */
.css.css, .property.property, .descriptor.descriptor {
color: #005a9c;
font-size: inherit;
font-family: inherit;
}
.css::before, .property::before, .descriptor::before {
content: "‘";
}
.css::after, .property::after, .descriptor::after {
content: "’";
}
.property, .descriptor {
/* Don't wrap property and descriptor names */
white-space: nowrap;
}
.type { /* CSS value <type> */
font-style: italic;
}
pre .property::before, pre .property::after {
content: "";
}
[data-link-type="property"]::before,
[data-link-type="propdesc"]::before,
[data-link-type="descriptor"]::before,
[data-link-type="value"]::before,
[data-link-type="function"]::before,
[data-link-type="at-rule"]::before,
[data-link-type="selector"]::before,
[data-link-type="maybe"]::before {
content: "‘";
}
[data-link-type="property"]::after,
[data-link-type="propdesc"]::after,
[data-link-type="descriptor"]::after,
[data-link-type="value"]::after,
[data-link-type="function"]::after,
[data-link-type="at-rule"]::after,
[data-link-type="selector"]::after,
[data-link-type="maybe"]::after {
content: "’";
}
[data-link-type].production::before,
[data-link-type].production::after,
.prod [data-link-type]::before,
.prod [data-link-type]::after {
content: "";
}
[data-link-type=element],
[data-link-type=element-attr] {
font-family: Menlo, Consolas, "DejaVu Sans Mono", monospace;
font-size: .9em;
}
[data-link-type=element]::before { content: "<" }
[data-link-type=element]::after { content: ">" }
[data-link-type=biblio] {
white-space: pre;
}</style>
<body class="h-entry">
<div class="head">
<p data-fill-with="logo"><a class="logo" href="http://www.w3.org/"> <img alt="W3C" height="48" src="https://www.w3.org/StyleSheets/TR/2016/logos/W3C" width="72"> </a> </p>
<h1>CSS Mobile Profile 2.0</h1>
<h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Editor’s Draft, <time class="dt-updated" datetime="2017-02-17">17 February 2017</time></span></h2>
<div data-fill-with="spec-metadata">
<dl>
<dt>This version:
<dd><a class="u-url" href="https://dev.w3.org/csswg/css-mobile/">https://dev.w3.org/csswg/css-mobile/</a>
<dt>Latest published version:
<dd><a href="https://www.w3.org/TR/css-mobile/">https://www.w3.org/TR/css-mobile/</a>
<dt>Previous Versions:
<dd><a href="https://www.w3.org/TR/2014/NOTE-css-mobile-20141014/" rel="previous">https://www.w3.org/TR/2014/NOTE-css-mobile-20141014/</a>
<dt class="editor">Editor:
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:bert@w3.org">Bert Bos</a> (<span class="p-org org">W3C</span>)
<dt>Issue Tracking:
<dd><span><a href="https://github.com/w3c/csswg-drafts/labels/css-mobile">GitHub Issues</a></span>
<dt>Previous editors:
<dd><span>Svante Schubert, Sun Microsystems Inc.</span>
<dd><span>Robin Berjon, Expway</span>
</dl>
</div>
<div data-fill-with="warning"></div>
<p class="copyright" data-fill-with="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2017 <a href="http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>, <a href="http://ev.buaa.edu.cn/">Beihang</a>). 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. </p>
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
<div class="p-summary" data-fill-with="abstract">
<p>
This specification defines in general a subset of
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1 <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a> that is
to be considered a baseline for interoperability between
implementations of
<acronym title="Cascading Style
Sheets">CSS</acronym>
on constrained devices (e.g. mobile phones).
Its intent is <em>not</em> to produce a profile of
<acronym title="Cascading Style Sheets">CSS</acronym>
incompatible with the
complete specification, but rather to ensure that implementations
that due to platform limitations cannot support the entire
specification implement a common subset that is interoperable not
only amongst constrained implementations but also with complete
ones. Additionally, this specification aligns itself as much as
possible with the
<acronym title="Open Mobile
Alliance">OMA</acronym>
Wireless
<acronym title="Cascading Style
Sheets">CSS</acronym>
1.1 <a data-link-type="biblio" href="#biblio-wcss11">[WCSS11]</a> specification. At the same
time,
<acronym title="Open Mobile Alliance">OMA</acronym>
is doing
alignment work in
<acronym title="Open Mobile
Alliance">OMA</acronym>
Wireless
<acronym title="Cascading Style
Sheets">CSS</acronym>
1.2 <a data-link-type="biblio" href="#biblio-wcss12">[WCSS12]</a>. It is aimed at aligning the
mandatory compliance items between
<acronym title="Cascading Style
Sheets">CSS</acronym>
Mobile Profile 2.0 and
<acronym title="Open
Mobile Alliance">OMA</acronym>
Wireless
<acronym title="Cascading
Style Sheets">CSS</acronym>
1.2 <a data-link-type="biblio" href="#biblio-wcss12">[WCSS12]</a>.
</p>
<p class="mtb"><strong>This profile is obsolete. Please see the latest <a href="https://www.w3.org/TR/CSS/">CSS Snapshot</a> for the
specifications that make up CSS.</strong></p>
<a href="http://www.w3.org/TR/CSS/">CSS</a> is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, in speech, etc.
</div>
<h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>
<div data-fill-with="status">
<p> This is a public copy of the editors’ draft.
It is provided for discussion only and may change at any moment.
Its publication here does not imply endorsement of its contents by W3C.
Don’t cite this document other than as work in progress. </p>
<p> <a href="https://github.com/w3c/csswg-drafts/issues">GitHub Issues</a> are preferred for discussion of this specification.
When filing an issue, please put the text “css-mobile” in the title,
preferably like this:
“[css-mobile] <i>…summary of comment…</i>”.
All issues and comments are <a href="https://lists.w3.org/Archives/Public/public-css-archive/">archived</a>,
and there is also a <a href="https://lists.w3.org/Archives/Public/www-style/">historical archive</a>. </p>
<p> This document was produced by the <a href="https://www.w3.org/Style/CSS/members">CSS Working Group</a> (part of the <a href="https://www.w3.org/Style/">Style Activity</a>). </p>
<p> This document was produced by a group operating under
the <a href="https://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent Policy</a>.
W3C maintains a <a href="https://www.w3.org/2004/01/pp-impl/32061/status" rel="disclosure">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="https://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a> must disclose the information in accordance with <a href="https://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the W3C Patent Policy</a>. </p>
<p> This document is governed by the <a href="https://www.w3.org/2015/Process-20150901/" id="w3c_process_revision">1 September 2015 W3C Process Document</a>. </p>
<p></p>
<p><em>At this time, the CSS Working Group does not envisage further
work on this specification and does not plan to propose it as a W3C
Recommendation.</em></p>
</div>
<div data-fill-with="at-risk"></div>
<nav data-fill-with="table-of-contents" id="toc">
<h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
<ol class="toc" role="directory">
<li><a href="#introduction"><span class="secno">1</span> <span class="content">Introduction</span></a>
<li><a href="#conf"><span class="secno">2</span> <span class="content">Conformance</span></a>
<li><a href="#selectors"><span class="secno">3</span> <span class="content">Selectors</span></a>
<li><a href="#at-rules"><span class="secno">4</span> <span class="content">At-rules</span></a>
<li><a href="#properties"><span class="secno">5</span> <span class="content">Properties</span></a>
<li><a href="#syntax"><span class="secno">6</span> <span class="content">Syntax</span></a>
<li><a href="#acknow"><span class="secno"></span> <span class="content">Acknowledgments</span></a>
<li>
<a href="#conformance"><span class="secno"></span> <span class="content"> Conformance</span></a>
<ol class="toc">
<li><a href="#document-conventions"><span class="secno"></span> <span class="content"> Document conventions</span></a>
<li><a href="#conform-classes"><span class="secno"></span> <span class="content"> Conformance classes</span></a>
<li>
<a href="#conform-responsible"><span class="secno"></span> <span class="content"> Requirements for Responsible Implementation of CSS</span></a>
<ol class="toc">
<li><a href="#conform-partial"><span class="secno"></span> <span class="content"> Partial Implementations</span></a>
<li><a href="#conform-future-proofing"><span class="secno"></span> <span class="content"> Implementations of Unstable and Proprietary Features</span></a>
<li><a href="#conform-testing"><span class="secno"></span> <span class="content"> Implementations of CR-level Features</span></a>
</ol>
</ol>
<li>
<a href="#references"><span class="secno"></span> <span class="content">References</span></a>
<ol class="toc">
<li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
<li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
</ol>
</ol>
</nav>
<main>
<p></p>
<title>CSS Mobile Profile 2.0</title>
<h2 class="heading settled" data-level="1" id="introduction"><span class="secno">1. </span><span class="content">Introduction</span><a class="self-link" href="#introduction"></a></h2>
<p>
This document specifies a profile of
<acronym title="Cascading Style Sheets">CSS</acronym>
that is in general based on
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1 <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a>, but requires as well new features from
<acronym title="Cascading Style Sheets">CSS</acronym>
3. In addition the document defines an <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> feature set, that is suggested to be implemented by more advanced user agents.
</p>
<h2 class="heading settled" data-level="2" id="conf"><span class="secno">2. </span><span class="content">Conformance</span><a class="self-link" href="#conf"></a></h2>
<p> The key words of
descriptive assertions and RFC 2119 terminology. The key words "MUST",
"MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in
RFC 2119 <a data-link-type="biblio" href="#biblio-rfc2119">[RFC2119]</a>. </p>
<p>
Since the goal of this specification is to define a baseline interoperability level, user
agents <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> accept
<acronym title="Cascading Style Sheets">CSS</acronym>
documents conforming to
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1 or subsequent revisions of the
<acronym title="Cascading Style Sheets">CSS</acronym>
family of Recommendations.
</p>
<p>
In order to conform to this specification, user agents, authoring tools, and content <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> conform to the <a href="http://www.w3.org/TR/CSS21/conform.html#conformance">Conformance</a> and <a href="http://www.w3.org/TR/CSS21/conform.html#errors">Error conditions</a> section of the
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1 specification <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a>, with the following modifications.
</p>
<ol>
<li>
Only features marked as supported in this specification are <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>.
Aside of the <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED </em> feature set,
an additional <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em> feature set is given, that may be implemented by more advanced user agents.
This feature set is <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> by the
<acronym title="Compound Document Formats">CDF</acronym>
as in <a data-link-type="biblio" href="#biblio-wicdmobile10">[WICDMobile10]</a>.
Support for a larger set of
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1 is <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>.
<li> The requirement concerning which <a href="http://www.w3.org/TR/CSS21/media.html"><acronym title="Cascading Style Sheets">CSS</acronym> 2.1 media types</a> are supported is tightened so that both the <code>handheld</code> and <code>all</code> media
types <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be accepted and processed. Other media types <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be accepted and processed as well.
<li> The requirements that user agents <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> make it possible to select an alternate style sheet
amongst those linked from the document, as well as provide for a way to turn off author style
sheets, are relaxed to be <em class="rfc2119" title="Keyword in RFC 2119 context">RECOMMENDED</em> behavior, but not <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>.
</ol>
<h2 class="heading settled" data-level="3" id="selectors"><span class="secno">3. </span><span class="content">Selectors</span><a class="self-link" href="#selectors"></a></h2>
<p>
Selectors are defined in the <a href="http://www.w3.org/TR/CSS21/selector.html">Selectors</a> chapter of the
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1 specification <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a>. The following table identifies which selector
constructs <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be supported amongst those defined by
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1.
</p>
<table class="features" summary="Selectors of CSS mobile profile 2.0">
<tbody>
<tr>
<th>Selector type
<th>Example
<th>Meaning
<th>Conformance
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#universal-selector">Universal selector</a>
<td><code>*</code>
<td>Matches any element.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#type-selectors">Type selectors</a>
<td><code>E</code>
<td>Matches any E element.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#descendant-selectors">Descendant selectors</a>
<td><code>E F</code>
<td>Matches any F element that is a descendant of an E element.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#child-selectors">Child selectors</a>
<td><code>E > F</code>
<td>Matches any F element that is a child of an element E.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#link-pseudo-classes">The link pseudo-classes</a>
<td><code>E:link</code>
<td>Matches element E if E is the source anchor of a hyperlink, unvisited by a user.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#link-pseudo-classes">The link pseudo-classes</a>
<td><code>E:visited</code>
<td>Matches element E if E is the source anchor of a hyperlink, visited by a user.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#dynamic-pseudo-classes">The dynamic pseudo-classes</a>
<td><code>E:active</code>
<td>Matches element E if E is being activated by the user.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#dynamic-pseudo-classes">The dynamic pseudo-classes</a>
<td><code>E:focus</code>
<td>Matches element E if E has the focus (accepts keyboard events or other forms of text input).
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#class-html">Class selectors</a>
<td><code>.warning</code>
<td> <em>Language specific</em>. (In (X)HTML, matches elements whose <code>class</code> attribute contains a
token with the same name.)
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#id-selectors">ID selectors</a>
<td><code>#myid</code>
<td>Matches any element with an ID equal to "myid".
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/selector.html#grouping">Grouping</a>
<td><code>E1, E2, E3 { ... }</code>
<td>Matches a group of elements, which share the same style declarations.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
</table>
<h2 class="heading settled" data-level="4" id="at-rules"><span class="secno">4. </span><span class="content">At-rules</span><a class="self-link" href="#at-rules"></a></h2>
<p>
At-rules are defined in the <a href="http://www.w3.org/TR/CSS21/syndata.html#at-rul
FEE3
es">at-rules</a> section of the
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1 specification <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a>. The following table identifies which at-rule
constructs <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be supported amongst those defined by
<acronym title="Cascading Style Sheets">CSS</acronym>
by setting the at-rule as <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> in the table’s last column.
Only at-rules that are part of the suggested feature set for advanced user agents are listed here as <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>.
</p>
<table class="features" summary="At-rules of CSS mobile profile 2.0">
<tbody>
<tr>
<th>Rule
<th>Definition
<th>Conformance
<tr>
<td><a href="http://www.w3.org/TR/CSS21/syndata.html#charset">@charset</a>
<td>Defines character encoding for the style sheet.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/cascade.html#at-import">@import</a>
<td>Imports an external style sheet.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td><a href="http://www.w3.org/TR/CSS21/media.html#at-media-rule">@media</a>
<td>Groups a set of style rules to apply only to one or more particular media. <br>Only the <code>handheld</code> and <code>all</code> media
types <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be accepted and processed. Other media types <em class="rfc2119" title="Keyword in RFC 2119 context">MAY</em> be accepted and processed as well.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr class="optional">
<td><a href="http://www.w3.org/TR/css3-namespace/#declaration">@namespace</a>
<td>For declaring the default namespace and binding namespaces to namespace prefixes.
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
</table>
<h2 class="heading settled" data-level="5" id="properties"><span class="secno">5. </span><span class="content">Properties</span><a class="self-link" href="#properties"></a></h2>
<p>
Properties are defined in several chapters of the
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1
specification <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a> and in case of marquee properties in the
<acronym title="Cascading Style Sheets">CSS</acronym>
Marquee Module <a data-link-type="biblio" href="#biblio-css3marquee">[CSS3MARQUEE]</a>. The following table identifies which properties <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> be supported amongst those defined by
<acronym title="Cascading Style Sheets">CSS</acronym>
by setting the property as <em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em> in the table’s last column.
Only properties that are part of the suggested feature set for advanced user agents are listed here as <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>.
The property syntax is provided (expressed using the same <a href="http://www.w3.org/TR/CSS21/about.html#value-defs">value specifications</a> as
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1) when it is subsetted from the original.
Limitations that apply to a property apply equally to its shorthand alternative.
</p>
<table class="features" summary="Properties of CSS mobile profile 2.0">
<tbody>
<tr>
<th>Property
<th>
Syntax (if different from
<acronym title="Cascading Style Sheets">CSS</acronym>
)
<th>Conformance
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background-color">background-color</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background-image">background-image</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background-repeat">background-repeat</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background-attachment">background-attachment</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background-position">background-position</a>
<td><code>top | center | bottom | left | right | inherit</code>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-background">background</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-top-width">border-top-width</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-right-width">border-right-width</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-bottom-width">border-bottom-width</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-left-width">border-left-width</a><br>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-width">border-width</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-top-color">border-top-color</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-right-color">border-right-color</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-bottom-color">border-bottom-color</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-left-color">border-left-color</a><br>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-color">border-color</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-top-style">border-top-style</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-right-style">border-right-style</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-bottom-style">border-bottom-style</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-left-style">border-left-style</a><br>
<td><code>none | solid | dashed | dotted | inherit</code>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-style">border-style</a>
<td><code>none | solid | dashed | dotted | inherit</code>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-top">border-top</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-right">border-right</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-bottom">border-bottom</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border-left">border-left</a><br>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-border">border</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr class="optional">
<td> <a href="http://www.w3.org/TR/CSS21/visuren.html#position-props">bottom</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visuren.html#propdef-clear">clear</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/colors.html#propdef-color">color</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visuren.html#propdef-display">display</a>
<td><code>inline | block | list-item | none | inherit</code>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visuren.html#propdef-float">float</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font-family">font-family</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font-style">font-style</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font-variant">font-variant</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font-weight">font-weight</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font-size">font-size</a>
<td><code><absolute-size> | <relative-size> | inherit</code>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/fonts.html#propdef-font">font</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-height">height</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr class="optional">
<td> <a href="http://www.w3.org/TR/CSS21/visuren.html#position-props">left</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/generate.html#propdef-list-style-type">list-style-type</a>
<td> <code>disc | circle | square | decimal | lower-roman | upper-roman | lower-alpha
| upper-alpha | none | inherit</code>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/generate.html#propdef-list-style-image">list-style-image</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/generate.html#propdef-list-style">list-style</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-margin-top">margin-top</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-margin-right">margin-right</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-margin-bottom">margin-bottom</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-margin-left">margin-left</a><br>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-margin">margin</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> marquee-direction <a data-link-type="biblio" href="#biblio-css3marquee">[CSS3MARQUEE]</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> marquee-loop <a data-link-type="biblio" href="#biblio-css3marquee">[CSS3MARQUEE]</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td>marquee-speed <a data-link-type="biblio" href="#biblio-css3marquee">[CSS3MARQUEE]</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td>marquee-style <a data-link-type="biblio" href="#biblio-css3marquee">[CSS3MARQUEE]</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-max-height">max-height</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-max-width">max-width</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-min-height">min-height</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-min-width">min-width</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr class="optional">
<td> <a href="http://www.w3.org/TR/CSS21/ui.html#propdef-outline-color">outline-color</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
<tr class="optional">
<td> <a href="http://www.w3.org/TR/CSS21/ui.html#propdef-outline-style">outline-style</a>
<td><code>none | solid | dashed | dotted | inherit</code>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
<tr class="optional">
<td> <a href="http://www.w3.org/TR/CSS21/ui.html#propdef-outline-width">outline-width</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
<tr class="optional">
<td> <a href="http://www.w3.org/TR/CSS21/ui.html#dynamic-outlines">outline</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
<tr>
<td> overflow <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a>
<td>auto
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> overflow-style <a data-link-type="biblio" href="#biblio-css3marquee">[CSS3MARQUEE]</a>
<td>marquee
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-padding-top">padding-top</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-padding-right">padding-right</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-padding-bottom">padding-bottom</a><br> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-padding-left">padding-left</a><br>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/box.html#propdef-padding">padding</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr class="optional">
<td> <a href="http://www.w3.org/TR/CSS21/visuren.html#choose-position">position</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
<tr class="optional">
<td> <a href="http://www.w3.org/TR/CSS21/visuren.html#position-props">right</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/text.html#propdef-text-indent">text-indent</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/text.html#propdef-text-align">text-align</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/text.html#propdef-text-decoration">text-decoration</a>
<td><code>none | blink |underline | inherit</code>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/text.html#propdef-text-transform">text-transform</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr class="optional">
<td> <a href="http://www.w3.org/TR/CSS21/visuren.html#position-props">top</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-vertical-align">vertical-align</a>
<td><code>top | middle | bottom | baseline | inherit</code>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visufx.html#propdef-visibility">visibility</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/text.html#propdef-white-space">white-space</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr>
<td> <a href="http://www.w3.org/TR/CSS21/visudet.html#propdef-width">width</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">REQUIRED</em>
<tr class="optional">
<td> <a href="http://www.w3.org/TR/CSS21/visuren.html#z-index">z-index</a>
<td>
<td><em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
</table>
<h3 class="no-num no-toc heading settled" id="informative-note"><span class="content">Informative Notes</span><a class="self-link" href="#informative-note"></a></h3>
<ul>
<li id="css-best-practise">
<a class="self-link" href="#css-best-practise"></a> Content Providers will reach a larger and more satisfied audience by following Mobile Web Best Practices <a data-link-type="biblio" href="#biblio-mobile-bp">[MOBILE-BP]</a> and
<acronym title="Cascading Style Sheets">CSS</acronym>
Techniques for Web Content Accessibility Guidelines <a data-link-type="biblio" href="#biblio-wcag10-css-techs">[WCAG10-CSS-TECHS]</a>.
<li id="wcss-extensions">
<a class="self-link" href="#wcss-extensions"></a> The
<acronym title="Open Mobile Alliance">OMA</acronym>
Wireless
<acronym title="Cascading Style Sheets">CSS</acronym>
1.1 <a data-link-type="biblio" href="#biblio-wcss11">[WCSS11]</a> introduced
three extensions <code>Marquee</code>, <code>Access Keys</code> and <code>Input</code>.
Those extensions are deprecated in
<acronym title="Open Mobile Alliance">OMA</acronym>
Wireless
<acronym title="Cascading Style Sheets">CSS</acronym>
1.2 <a data-link-type="biblio" href="#biblio-wcss12">[WCSS12]</a>. The <code>Marquee</code> functionality has been redefined by the marquee properties of the
<acronym title="Cascading Style Sheets">CSS</acronym>
3 box model <a data-link-type="biblio" href="#biblio-css3marquee">[CSS3MARQUEE]</a>
</ul>
<h2 class="heading settled" data-level="6" id="syntax"><span class="secno">6. </span><span class="content">Syntax</span><a class="self-link" href="#syntax"></a></h2>
<p>
A user agent <em class="rfc2119" title="Keyword in RFC 2119 context">MUST</em> support all value types defined in the <a href="http://www.w3.org/TR/CSS21/syndata.html#values">Values</a> section of the
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1 specification <a data-link-type="biblio" href="#biblio-css21">[CSS21]</a>, with the following exceptions:
</p>
<ol>
<li>Support for <a href="http://www.w3.org/TR/CSS21/syndata.html#counter">counter values</a> is <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>
<li> Support for <a href="http://www.w3.org/TR/CSS21/ui.html#system-colors">CSS2 System Colors</a> and <a href="http://www.w3.org/TR/CSS21/ui.html#system-fonts">User preferences for fonts</a> is <em class="rfc2119" title="Keyword in RFC 2119 context">OPTIONAL</em>.
</ol>
<h2 class="no-num heading settled" id="acknow"><span class="content">Acknowledgments</span><a class="self-link" href="#acknow"></a></h2>
<p>
The editors wish to thank the authors of the previous version of this document,
Ted Wugofski (Openwave), Doug Dominiak (Openwave, formerly Motorola),
Peter Stark (Ericsson), and Tapas Roy (Openwave), as well as the authors of
the
<acronym title="Open Mobile Alliance">OMA</acronym>
Wireless
<acronym title="Cascading Style Sheets">CSS</acronym>
specifications and the
<acronym title="Cascading Style Sheets">CSS</acronym>
2.1 specification.
Furthermore, the editors want to thank the
<acronym title="Compound Document Formats">CDF</acronym>
<acronym title="Working Group">WG</acronym>
for their participation on this specification.
</p>
</main>
<h2 class="no-ref no-num heading settled" id="conformance"><span class="content"> Conformance</span><a class="self-link" href="#conformance"></a></h2>
<h3 class="heading settled" id="document-conventions"><span class="content"> Document conventions</span><a class="self-link" href="#document-conventions"></a></h3>
<p>Conformance requirements are expressed with a combination of
descriptive assertions and RFC 2119 terminology. The key words “MUST”,
“MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
“RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
document are to be interpreted as described in RFC 2119.
However, for readability, these words do not appear in all uppercase
letters in this specification. </p>
<p>All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119">[RFC2119]</a> </p>
<p>Examples in this specification are introduced with the words “for example”
or are set apart from the normative text with <code>class="example"</code>,
like this: </p>
<div class="example" id="example-52448c84">
<a class="self-link" href="#example-52448c84"></a>
<p>This is an example of an informative example. </p>
</div>
<p>Informative notes begin with the word “Note” and are set apart from the
normative text with <code>class="note"</code>, like this: </p>
<p class="note" role="note">Note, this is an informative note. </p>
<p>Advisements are normative sections styled to evoke special attention and are
set apart from other normative text with <code><strong class="advisement"></code>, like
this: <strong class="advisement"> UAs MUST provide an accessible alternative. </strong> </p>
<h3 class="heading settled" id="conform-classes"><span class="content"> Conformance classes</span><a class="self-link" href="#conform-classes"></a></h3>
<p>Conformance to this specification
is defined for three conformance classes: </p>
<dl>
<dt>style sheet
<dd>A <a href="http://www.w3.org/TR/CSS2/conform.html#style-sheet">CSS
style sheet</a>.
<dt>renderer
<dd>A <a href="http://www.w3.org/TR/CSS2/conform.html#user-agent">UA</a> that interprets the semantics of a style sheet and renders
documents that use them.
<dt>authoring tool
<dd>A <a href="http://www.w3.org/TR/CSS2/conform.html#user-agent">UA</a> that writes a style sheet.
</dl>
<p>A style sheet is conformant to this specification
if all of its statements that use syntax defined in this module are valid
according to the generic CSS grammar and the individual grammars of each
feature defined in this module. </p>
<p>A renderer is conformant to this specification
if, in addition to interpreting the style sheet as defined by the
appropriate specifications, it supports all the features defined
by this specification by parsing them correctly
and rendering the document accordingly. However, the inability of a
UA to correctly render a document due to limitations of the device
does not make the UA non-conformant. (For example, a UA is not
required to render color on a monochrome monitor.) </p>
<p>An authoring tool is conformant to this specification
if it writes style sheets that are syntactically correct according to the
generic CSS grammar and the individual grammars of each feature in
this module, and meet all other conformance requirements of style sheets
as described in this module. </p>
<h3 class="heading settled" id="conform-responsible"><span class="content"> Requirements for Responsible Implementation of CSS</span><a class="self-link" href="#conform-responsible"></a></h3>
<p>The following sections define several conformance requirements
for implementing CSS responsibly,
in a way that promotes interoperability in the present and future. </p>
<h4 class="heading settled" id="conform-partial"><span class="content"> Partial Implementations</span><a class="self-link" href="#conform-partial"></a></h4>
<p>So that authors can exploit the forward-compatible parsing rules to assign fallback values, <strong>CSS renderers <em>must</em> treat as invalid
(and <a href="http://www.w3.org/TR/CSS2/conform.html#ignore">ignore as appropriate</a>)
any at-rules, properties, property values, keywords, and other syntactic constructs
for which they have no usable level of support</strong>.
In particular, user agents <em>must not</em> selectively ignore
unsupported property values and honor supported values in a single multi-value property declaration:
if any value is considered invalid (as unsupported values must be),
CSS requires that the entire declaration be ignored. </p>
<h4 class="heading settled" id="conform-future-proofing"><span class="content"> Implementations of Unstable and Proprietary Features</span><a class="self-link" href="#conform-future-proofing"></a></h4>
<p>To avoid clashes with future stable CSS features,
the CSSWG recommends <a href="http://www.w3.org/TR/CSS/#future-proofing">following best practices</a> for the implementation of <a href="http://www.w3.org/TR/CSS/#unstable">unstable</a> features and <a href="http://www.w3.org/TR/CSS/#proprietary-extension">proprietary extensions</a> to CSS. </p>
<h4 class="heading settled" id="conform-testing"><span class="content"> Implementations of CR-level Features</span><a class="self-link" href="#conform-testing"></a></h4>
<p>Once a specification reaches the Candidate Recommendation stage,
implementers should release an <a data-link-type="dfn" href="http://www.w3.org/TR/CSS/#vendor-prefix">unprefixed</a> implementation
of any CR-level feature they can demonstrate
to be correctly implemented according to spec,
and should avoid exposing a prefixed variant of that feature. </p>
<p>To establish and maintain the interoperability of CSS across
implementations, the CSS Working Group requests that non-experimental
CSS renderers submit an implementation report (and, if necessary, the
testcases used for that implementation report) to the W3C before
releasing an unprefixed implementation of any CSS features. Testcases
submitted to W3C are subject to review and correction by the CSS
Working Group. </p>
<p>
Further information on submitting testcases and implementation reports
can be found from on the CSS Working Group’s website at <a href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
Questions should be directed to the <a href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a> mailing list.
<script src="https://www.w3.org/scripts/TR/2016/fixup.js"></script>
</p>
<h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
<h3 class="no-num no-ref heading settled" id="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3>
<dl>
<dt id="biblio-css21">[CSS21]
<dd>Bert Bos; et al. <a href="https://www.w3.org/TR/CSS2">Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification</a>. 7 June 2011. REC. URL: <a href="https://www.w3.org/TR/CSS2">https://www.w3.org/TR/CSS2</a>
<dt id="biblio-css3marquee">[CSS3MARQUEE]
<dd>Bert Bos. <a href="https://www.w3.org/TR/css3-marquee">CSS Marquee Module Level 3</a>. 14 October 2014. NOTE. URL: <a href="https://www.w3.org/TR/css3-marquee">https://www.w3.org/TR/css3-marquee</a>
<dt id="biblio-rfc2119">[RFC2119]
<dd>S. Bradner. <a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>. March 1997. Best Current Practice. URL: <a href="https://tools.ietf.org/html/rfc2119">https://tools.ietf.org/html/rfc2119</a>
<dt id="biblio-wicdmobile10">[WICDMobile10]
<dd>Timur Mehrvarz; et al. <a href="https://www.w3.org/TR/WICDMobile/">WICD Mobile 1.0</a>. 19 August 2010. NOTE. URL: <a href="https://www.w3.org/TR/WICDMobile/">https://www.w3.org/TR/WICDMobile/</a>
</dl>
<h3 class="no-num no-ref heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3>
<dl>
<dt id="biblio-mobile-bp">[MOBILE-BP]
<dd>Jo Rabin; Charles McCathieNevile. <a href="https://www.w3.org/TR/mobile-bp/">Mobile Web Best Practices 1.0</a>. 29 July 2008. REC. URL: <a href="https://www.w3.org/TR/mobile-bp/">https://www.w3.org/TR/mobile-bp/</a>
<dt id="biblio-wcag10-css-techs">[WCAG10-CSS-TECHS]
<dd>Wendy Chisholm; Gregg Vanderheiden; Ian Jacobs. <a href="https://www.w3.org/TR/WCAG10-CSS-TECHS/">CSS Techniques for Web Content Accessibility Guidelines 1.0</a>. 6 November 2000. NOTE. URL: <a href="https://www.w3.org/TR/WCAG10-CSS-TECHS/">https://www.w3.org/TR/WCAG10-CSS-TECHS/</a>
<dt id="biblio-wcss11">[WCSS11]
<dd>Open Mobile Alliance. <a href="http://www.openmobilealliance.org/technical/release_program/docs/Browsing/V2_3-20080331-A/OMA-WAP-WCSS-V1_1-20061020-A.pdf"><cite>Wireless CSS Specification.</cite></a> October 2006. Approved Version 1.1. URL: <a href="http://www.openmobilealliance.org/technical/release_program/docs/Browsing/V2_3-20080331-A/OMA-WAP-WCSS-V1_1-20061020-A.pdf">http://www.openmobilealliance.org/technical/release_program/docs/Browsing/V2_3-20080331-A/OMA-WAP-WCSS-V1_1-20061020-A.pdf</a>
<dt id="biblio-wcss12">[WCSS12]
<dd>Open Mobile Alliance. <a href="http://www.openmobilealliance.org/ftp/Public_documents/MCE/MAE/Permanent_documents/OMA-TS-WCSS-V1_2-20070921-D.zip"><cite>Wireless CSS Specification Version 1.2.</cite></a> 21 September 2007. (Work in progress.) URL: <a href="http://www.openmobilealliance.org/ftp/Public_documents/MCE/MAE/Permanent_documents/OMA-TS-WCSS-V1_2-20070921-D.zip">http://www.openmobilealliance.org/ftp/Public_documents/MCE/MAE/Permanent_documents/OMA-TS-WCSS-V1_2-20070921-D.zip</a>
</dl>
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