-
Notifications
You must be signed in to change notification settings - Fork 790
Expand file tree
/
Copy pathOverview.html
More file actions
904 lines (894 loc) · 56 KB
/
Overview.html
File metadata and controls
904 lines (894 loc) · 56 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
<!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=&q
6901
uot;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&g
20D
t;<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-rules">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
6D23
”,
“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/CSS
4A5C
2</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>