csswg-drafts/cssom/Overview.html at 42e60e0e7e3fb12fd799a9cca26a12426f3d9c35 · w3c/csswg-drafts · GitHub

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
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
<!DOCTYPE html><html lang="en-US"><head>
  <meta charset="utf-8">
  <title>CSS Object Model (CSSOM)</title>
  <link href="cssom.css" rel="stylesheet">
  <link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet">
 </head>
 <body class="draft">
  <div class="head">

<!--begin-logo-->
<p><a href="http://www.w3.org/"><img alt="W3C" height="48" src="http://www.w3.org/Icons/w3c_home" width="72"></a></p>
<!--end-logo-->

   <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
   <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

   <h1 id="cssom">CSS Object Model (CSSOM)</h1>

   <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

   <h2 class="no-num no-toc" id="w3c-doctype">Editor's Draft 13 August 2012</h2>

   <dl>

    <dt>This Version:</dt>
    <dd class="dontpublish"><a href="http://dvcs.w3.org/hg/csswg/raw-file/tip/cssom/Overview.html">http://dvcs.w3.org/hg/csswg/raw-file/tip/cssom/Overview.html</a></dd>
    <dt class="dontpublish">Participate:</dt>
    <dd class="dontpublish"><a href="mailto:www-style@w3.org?subject==%5Bcssom%5D%20">www-style@w3.org<
8DE3
/a> (<a href="http://lists.w3.org/Archives/Public/www-style/">archives</a>)</dd>
    <dd class="dontpublish"><a href="https://www.w3.org/Bugs/Public/enter_bug.cgi?product=CSS&amp;component=CSSOM">File a bug</a></dd>
    <dd class="dontpublish"><a href="http://wiki.whatwg.org/wiki/IRC">IRC: #css on Freenode</a></dd>

    <dt class="dontpublish">Previous Version:</dt>
    <dd class="dontpublish"><a href="http://www.w3.org/TR/2011/WD-cssom-20110712/">http://www.w3.org/TR/2011/WD-cssom-20110712/</a></dd>
    <dd class="dontpublish"><a href="http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/">http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/</a></dd>

    <dt>Editors:</dt>
    <dd><a href="http://www.w3.org/wiki/User:Gadams">Glenn Adams</a>
    (<a href="http://www.cox.com/">Cox Communications, Inc.</a>)
    &lt;<a href="mailto:glenn.adams@cox.com">glenn.adams@cox.com</a>&gt;</dd>
    <dd><a>Shane Stephens</a>
    (<a href="http://www.google.com/">Google, Inc.</a>)
    &lt;<a href="mailto:shans@google.com">shans@google.com</a>&gt;</dd>

    <dt>Previous Editor:</dt>
    <dd><a href="http://annevankesteren.nl/">Anne van Kesteren</a>
    (<a href="http://www.opera.com/">Opera Software ASA</a>)
    &lt;<a href="mailto:annevk@opera.com">annevk@opera.com</a>&gt;</dd>
   </dl>


<!--begin-copyright-->
<p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2012 <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>), All Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.</p>
<!--end-copyright-->

  </div>

  <hr class="top">

  <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

  <h2 class="no-num no-toc" id="abstract">Abstract</h2>

  <p>CSSOM defines APIs (including generic parsing and serialization rules)
  for Media Queries, Selectors, and of course CSS itself.</p>

  <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

  <h2 class="no-num no-toc" id="sotd">Status of this Document</h2>

  <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 or by the CSS Working Group. Don't cite
  this document other than as work in progress.</p>

  <p class="note">Implementers should note well that this specification is an ongoing effort to sort out
  what has been widely implemented and deployed from DOM-2 Style as well as common extensions thereto, some details
  of which are currently interoperable and others which are not currently interoperable. As this specification moves
  forward, it is hoped that these differences will be resolved and an unambiguous and adequate consensus-based
  specification will emerge.</p>

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

  <p class="dontpublish">This is the 13 August 2012 Editor's Draft of CSSOM. Please send comments to
  <a href="mailto:www-style@w3.org?subject=%5Bcssom%5D%20">www-style@w3.org</a>
  (<a href="http://lists.w3.org/Archives/Public/www-style/">archived</a>)
  with <samp>[cssom]</samp> at the start of the subject line.

  <p>This document was produced by a group operating under the
  <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent Policy</a>.
  W3C maintains a
  <a href="http://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="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a>
  must disclose the information in accordance with
  <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the W3C Patent Policy</a>.</p>

  <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

  <h2 class="no-num no-toc" id="toc">Table of Contents</h2>


<!--begin-toc-->
<ol class="toc">
 <li><a href="#introduction"><span class="secno">1 </span>Introduction</a>
  <ol class="toc">
   <li><a href="#history"><span class="secno">1.1 </span>History</a></ol></li>
 <li><a href="#conformance"><span class="secno">2 </span>Conformance</a></li>
 <li><a href="#terminology"><span class="secno">3 </span>Terminology</a>
  <ol class="toc">
   <li><a href="#common-serializing-idioms"><span class="secno">3.1 </span>Common Serializing Idioms</a></ol></li>
 <li><a href="#media-queries"><span class="secno">4 </span>Media Queries</a>
  <ol class="toc">
   <li><a href="#parsing-media-queries"><span class="secno">4.1 </span>Parsing Media Queries</a></li>
   <li><a href="#serializing-media-queries"><span class="secno">4.2 </span>Serializing Media Queries</a>
    <ol class="toc">
     <li><a href="#serializing-media-feature-values"><span class="secno">4.2.1 </span>Serializing Media Feature Values</a></ol></li>
   <li><a href="#comparing-media-queries"><span class="secno">4.3 </span>Comparing Media Queries</a></li>
   <li><a href="#the-medialist-interface"><span class="secno">4.4 </span>The <code>MediaList</code> Interface</a></ol></li>
 <li><a href="#selectors"><span class="secno">5 </span>Selectors</a>
  <ol class="toc">
   <li><a href="#parsing-selectors"><span class="secno">5.1 </span>Parsing Selectors</a></li>
   <li><a href="#serializing-selectors"><span class="secno">5.2 </span>Serializing Selectors</a></ol></li>
 <li><a href="#css"><span class="secno">6 </span>CSS</a>
  <ol class="toc">
   <li><a href="#style-sheet-0"><span class="secno">6.1 </span>Style Sheet</a>
    <ol class="toc">
     <li><a href="#the-stylesheet-interface"><span class="secno">6.1.1 </span>The <code>StyleSheet</code> Interface</a></li>
     <li><a href="#the-cssstylesheet-interface"><span class="secno">6.1.2 </span>The <code>CSSStyleSheet</code> Interface</a></ol></li>
   <li><a href="#style-sheet-collections"><span class="secno">6.2 </span>Style Sheet Collections</a>
    <ol class="toc">
     <li><a href="#the-http-default-style-header"><span class="secno">6.2.1 </span>The HTTP <code>Default-Style</code> Header</a></li>
     <li><a href="#the-stylesheetlist-sequence"><span class="secno">6.2.2 </span>The <code>StyleSheetList</code> Sequence</a></li>
     <li><a href="#extensions-to-the-document-interface"><span class="secno">6.2.3 </span>Extensions to the <code>Document</code> Interface</a></li>
     <li><a href="#interaction-with-the-user-interface"><span class="secno">6.2.4 </span>Interaction with the User Interface</a>
      <ol class="toc">
       <li><a href="#persisting-the-selected-style-sheet-set"><span class="secno">6.2.4.1 </span>Persisting the selected style sheet set</a></ol></li>
     <li><a href="#examples"><span class="secno">6.2.5 </span>Examples</a></ol></li>
   <li><a href="#style-sheet-association"><span class="secno">6.3 </span>Style She
7DDD
et Association</a>
    <ol class="toc">
     <li><a href="#the-linkstyle-interface"><span class="secno">6.3.1 </span>The <code>LinkStyle</code> Interface</a></li>
     <li><a href="#requirements-on-specifications"><span class="secno">6.3.2 </span>Requirements on specifications</a></li>
     <li><a href="#requirements-on-user-agents-implementing-the-xml-stylesheet-processing-instruction"><span class="secno">6.3.3 </span>Requirements on User Agents Implementing the
  <span><code>xml-stylesheet</code> processing instruction</span></a></li>
     <li><a href="#requirements-on-user-agents-implementing-the-http-link-header"><span class="secno">6.3.4 </span>Requirements on User Agents Implementing the HTTP
  <code>Link</code> Header</a></ol></li>
   <li><a href="#css-rules"><span class="secno">6.4 </span>CSS Rules</a>
    <ol class="toc">
     <li><a href="#the-cssrulelist-sequence"><span class="secno">6.4.1 </span>The <code>CSSRuleList</code> Sequence</a></li>
     <li><a href="#the-cssrule-interface"><span class="secno">6.4.2 </span>The <code>CSSRule</code> Interface</a></li>
     <li><a href="#the-cssstylerule-interface"><span class="secno">6.4.3 </span>The <code>CSSStyleRule</code> Interface</a></li>
     <li><a href="#the-cssimportrule-interface"><span class="secno">6.4.4 </span>The <code>CSSImportRule</code> Interface</a></li>
     <li><a href="#the-cssmediarule-interface"><span class="secno">6.4.5 </span>The <code>CSSMediaRule</code> Interface</a></li>
     <li><a href="#the-cssfontfacerule-interface"><span class="secno">6.4.6 </span>The <code>CSSFontFaceRule</code> Interface</a></li>
     <li><a href="#the-csspagerule-interface"><span class="secno">6.4.7 </span>The <code>CSSPageRule</code> Interface</a></li>
     <li><a href="#the-cssnamespacerule-interface"><span class="secno">6.4.8 </span>The <code>CSSNamespaceRule</code> Interface</a></ol></li>
   <li><a href="#css-declaration-blocks"><span class="secno">6.5 </span>CSS Declaration Blocks</a>
    <ol class="toc">
     <li><a href="#the-cssstyledeclaration-interface"><span class="secno">6.5.1 </span>The <code>CSSStyleDeclaration</code> Interface</a></ol></li>
   <li><a href="#css-values"><span class="secno">6.6 </span>CSS Values</a>
    <ol class="toc">
     <li><a href="#parsing-css-values"><span class="secno">6.6.1 </span>Parsing CSS Values</a></li>
     <li><a href="#serializing-css-values"><span class="secno">6.6.2 </span>Serializing CSS Values</a>
      <ol class="toc">
       <li><a href="#examples-0"><span class="secno">6.6.2.1 </span>Examples</a></ol></ol></ol></li>
 <li><a href="#dom-access-to-css-declaration-blocks"><span class="secno">7 </span>DOM Access to CSS Declaration Blocks</a>
  <ol class="toc">
   <li><a href="#the-elementcssinlinestyle-interface"><span class="secno">7.1 </span>The <code>ElementCSSInlineStyle</code> Interface</a></li>
   <li><a href="#extensions-to-the-window-interface"><span class="secno">7.2 </span>Extensions to the <code>Window</code> Interface</a></ol></li>
 <li><a href="#resolved-values"><span class="secno">8 </span>Resolved Values</a></li>
 <li><a href="#iana-considerations"><span class="secno">9 </span>IANA Considerations</a>
  <ol class="toc">
   <li><a href="#default-style"><span class="secno">9.1 </span><code>Default-Style</code></a></ol></li>
 <li><a class="no-num" href="#references">References</a>
  <ol class="toc">
   <li><a class="no-num" href="#normative-references">Normative references</a></li>
   <li><a class="no-num" href="#informative-references">Informative references</a></ol></li>
 <li><a class="no-num" href="#acknowledgments">Acknowledgments</a></ol>
<!--end-toc-->

  <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

  <h2 id="introduction"><span class="secno">1 </span>Introduction</h2>

  <p class="issue">...</p>

  <!-- ........................................................................................................................ -->
  <!-- ........................................................................................................................ -->

  <h3 id="history"><span class="secno">1.1 </span>History</h3>

  <p>Several interfaces from DOM Level 2 Style
  <a href="http://lists.w3.org/Archives/Public/www-style/2003Oct/0347.html" title="[CSSOM] CSSValue and related interfaces (message from the CSS WG)">have
  been obsoleted</a> because they were thought to be too awkward for
  frequent use. This specification no longer contains those features.
  <code>DOMImplementationCSS</code> and <code>CSSCharsetRule</code> have
  been removed as well as they were not deemed necessary.</p>

  <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

  <h2 id="conformance"><span class="secno">2 </span>Conformance</h2>

  <p>All diagrams, examples, and notes in this specification are
  non-normative, as are all sections explicitly marked non-normative.
  Everything else in this specification is normative.

  <p>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 RFC2119. For readability, these words do
  not appear in all uppercase letters in this specification.
  <a href="#refsRFC2119">[RFC2119]</a>

  <p>Requirements phrased in the imperative as part of algorithms
  (such as "strip any leading space characters" or "return false and
  terminate these steps") are to be interpreted with the meaning of the
  key word ("must", "should", "may", etc) used in introducing the
  algorithm.

  <p>Conformance requirements phrased as algorithms or specific steps
  may be implemented in any manner, so long as the end result is
  equivalent. (In particular, the algorithms defined in this
  specification are intended to be easy to follow, and not intended to
  be performant.)

  <p id="hardwareLimitations">User agents may impose
  implementation-specific limits on otherwise unconstrained inputs,
  e.g. to prevent denial of service attacks, to guard against running
  out of memory, or to work around platform-specific limitations.

  <p>When a method or an attribute is said to call another method or attribute, the user agent must invoke its internal API for that attribute or method so that e.g. the author can't change the behavior by overriding attributes or methods with custom properties or functions in ECMAScript.

  <p>Unless otherwise stated, string comparisons are done in a
  <a class="external" href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#case-sensitive">case-sensitive</a> manner.

  <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

  <h2 id="terminology"><span class="secno">3 </span>Terminology</h2>

  <p>Terminology used in this specification is from
  <cite>DOM4</cite>,
  <cite>Associating Style Sheets with XML documents</cite>
  and
  <cite>XML</cite>
  <a href="#refsDOM">[DOM]</a>
  <a href="#refsHTML">[HTML]</a>
  <a href="#refsXMLSS">[XMLSS]</a>
  <a href="#refsXML">[XML]</a>

  <p class="issue"><dfn id="supported-styling-language">supported styling language</dfn>

  <p>When this specification talks about object
  <code><var>A</var></code> where <code><var>A</var></code> is actually an interface, it generally means an object implementing interface
  <code><var>A</var></code>.</p>

  <p>The term <dfn id="whitespace">whitespace</dfn> is used as defined in CSS.
  <!--XXX <a href="#ref-css">[CSS]</a>--></p>

  <!-- ........................................................................................................................ -->
  <!-- ........................................................................................................................ -->

  <h3 id="common-serializing-idioms"><span class="secno">3.1 </span>Common Serializing Idioms</h3>

  <p>To <dfn id="serialize-a-character">serialize a character</dfn> means to create a string of
  "<code>\</code>" (U+005C), followed by the character.</p>

  <p>To <dfn id="serialize-a-character-as-code-point">serialize a character as code point</dfn> means to create a
  string of "<code>\</code>" (U+005C), followed by the Unicode code point as
  the smallest possible number of hexadecimal digits in the range 0-9 a-f
  (U+0030 to U+0039 and U+0061 to U+0066) to represent the code point in
  base 16, followed by a space (U+0020).</p>

  <p>To <dfn id="serialize-an-identifier">serialize an identifier</dfn> means to create a string represented
  by the concatenation of, for each character of the identifier:</p>

  <ul>
   <li>If the character is in the range U+0000 to U+001F or U+007F to
   U+009F, the character
   <a href="#serialize-a-character-as-code-point" title="serialize a character as code point">escaped as code point</a>.</li>
   <li>If the character is the first character and is in the range 0-9
   (U+0030 to U+0039), the character
   <a href="#serialize-a-character-as-code-point" title="serialize a character as code point">escaped as code point</a>.</li>
   <li>If the character is the second character and is in the range 0-9
   (U+0030 to U+0039) and the first character is a "<code>-</code>"
   (U+002D), the character
   <a href="#serialize-a-character-as-code-point" title="serialize a character as code point">escaped as code point</a>.</li>
   <li>If the character is the second character and is "<code>-</code>"
   (U+002D) and the first character is "<code>-</code>" too, the
   <a href="#serialize-a-character" title="serialize a character">escaped</a> character.</li>
   <li>If the character is not handled by one of the above rules and is
   greater than or equal to U+0080, is "<code>-</code>" (U+002D) or
   "<code>_</code>" (U+005F), or is in one of the ranges 0-9 (U+0030 to
   U+0039), A-Z (U+0041 to U+005A), or a-z (U+0061 to U+007A), the character
   itself.</li>
   <li>Otherwise, the <a href="#serialize-a-character" title="serialize a character">escaped</a>
   character.</li>
  </ul>

  <p>To <dfn id="serialize-a-string">serialize a string</dfn> means to create a string represented
  by '<code>"</code>' (U+0022), followed by the result of applying the rules
  below to each character of the given string, followed by
  '<code>"</code>' (U+0022):</p>

  <ul>
   <li>If the character is in the range U+0000 to U+001F or U+007F to
   U+009F, the character
   <a href="#serialize-a-character-as-code-point" title="serialize a character as code point">escaped as code point</a>.</li>
   <li>If the character is '<code>"</code>' (U+0022) or '<code>\</code>'
   (U+005C), the <a href="#serialize-a-character" title="serialize a character">escaped</a> character.</li>
   <li>Otherwise, the character itself.</li>
  </ul>

  <p class="note">"<code>'</code>" (U+0027) is not escaped because strings
  are always serialized with '<code>"</code>' (U+0022).</p>

  <p>To <dfn id="serialize-a-url">serialize a URL</dfn> means to create a string represented by
  "<code>url(</code>", followed by the
  <a href="#serialize-a-string" title="serialize a string">string escaped</a> value of the given
  string, followed by "<code>)</code>".</p>

  <p>To <dfn id="serialize-a-comma-separated-list">serialize a comma-separated list</dfn> concatenate all items of
  the list in list order while separating them by "<code>,</code>" (U+002C),
  followed by a space (U+0020).</p>

  <p>To <dfn id="serialize-a-whitespace-separated-list">serialize a whitespace-separated list</dfn> concatenate all
  items of the list in list order while separating them a space (U+0020).</p>

  <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

  <h2 id="media-queries"><span class="secno">4 </span>Media Queries</h2>

  <p>Media queries are defined by the Media Queries specification. This
  section defines various concepts around media queries, including their API
  and serialization form.</p>

  <!-- XXX ref -->

  <!-- ........................................................................................................................ -->
  <!-- ........................................................................................................................ -->

  <h3 id="parsing-media-queries"><span class="secno">4.1 </span>Parsing Media Queries</h3>

  <p>To
  <dfn id="parse-a-media-query-list">parse a media query list</dfn> for a
  given string <var>s</var> into a media query list is defined in
  the Media Queries specification. Return the list of one or more media
  queries that the algorithm defined there gives.</p> <!-- XXX ref -->

  <p class="note">A media query that ends up being "ignored" will turn
  into "<code>not all</code>".</p>

  <p>To
  <dfn id="parse-a-media-query">parse a media query</dfn> for a given string
  <var>s</var> means to follow the
  <a href="#parse-a-media-query-list">parse a media query list</a> steps and return null if more
  than one media query is returned or a media query if a
  single media query is returned.</p>

  <p class="note">Again, a media query that ends up being "ignored" will
  turn into "<code>not all</code>".</p>

  <!-- ........................................................................................................................ -->

  <h3 id="serializing-media-queries"><span class="secno">4.2 </span>Serializing Media Queries</h3>

  <p>To
  <dfn id="serialize-a-media-query-list">serialize a media query list</dfn>
  run these steps:</p>

  <ol>
   <li><p>If the media query list is empty return the empty string and
   terminate these steps.</li>

   <li><p><a href="#serialize-a-media-query" title="serialize a media query">Serialize</a> each
   media query in the list of media queries, sort them in lexicographical
   order, and then
   <a href="#serialize-a-comma-separated-list" title="serialize a comma-separated list">serialize</a> the
   list.</li>
  </ol>

  <p>To
  <dfn id="serialize-a-media-query">serialize a media query</dfn> let
  <var>s</var> be the empty string, run the steps below, and
  finally return <var>s</var>:</p>

  <ol>
   <li><p>If the media query is negated append "<code>not</code>", followed
   by a space (U+0020), to <var>s</var>.</li>

   <li><p>Let <var>type</var> be the media type of the media query,
   <a href="#serialize-an-identifier" title="serialize an identifier">escaped</a> and
   <a class="external" href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#converted-to-ascii-lowercase">converted to ASCII lowercase</a>.</li>

   <li><p>If the media query does not contain media features append
   <var>type</var>, to <var>s</var>,
   then return <var>s</var> and terminate this algorithm.</li>

   <li><p>If <var>type</var> is not "<code>all</code>" or if the
   media query is negated append <var>type</var>, followed by a
   space (U+0020), followed by "<code>and</code>", followed by a space
   (U+0020), to <var>s</var>.</li>

   <li><p>Sort the media features in lexicographical order.</li>

   <li>
    <p>Then, for each media feature:</p>

    <ol>
     <li>Append a "<code>(</code>" (U+0028), followed by the media feature
     name, <a class="external" href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#converted-to-ascii-lowercase">converted to ASCII lowercase</a>,
     to <var>s</var>.<p></li>

     <li><p>If a value is given append a "<code>:</code>" (U+003A), followed
     by a space (U+0020), followed by the
     <a href="#serialize-a-media-feature-value" title="serialize a media feature value">serialized media feature value</a>,
     to <var>s</var>.</li>

     <li><p>Append a "<code>)</code>" (U+0029) to
     <var>s</var>.</li>

     <li><p>If this is not the last media feature append a space (U+0020),
     followed by "<code>and</code>", followed by a space (U+0020), to
     <var>s</var>.</li>
    </ol>
   </li>
  </ol>

  <div class="example">
   <p>Here are some examples of input (first column) and output (second
   column):</p>

   <table>
    <thead>
     <tr><th>Input<th>Output
    <tbody>
     <tr>
      <td><code>not screen and (min-WIDTH:5px) AND (max-width:40px  )</code>
      <td><code>not screen and (max-width: 40px) and (min-width: 5px)</code>
     <tr>
      <td><code>all and (color) and (color)</code>
      <td><code>(color)</code>
   </table>
  </div>


  <!-- ........................................................................................................................ -->

  <h4 id="serializing-media-feature-values"><span class="secno">4.2.1 </span>Serializing Media Feature Values</h4>

  <p class="issue">This should probably be done in terms of mapping it to
  serializing CSS values as media features are defined in terms of CSS
  values after all.</p>

  <p>To <dfn id="serialize-a-media-feature-value">serialize a media feature value</dfn>
  named <var>v</var> locate <var>v</var> in the first
  column of the table below and use the serialization format described in
  the second column:</p>

  <table>
   <tr>
    <th>Media Feature
    <th>Serialization
   <tr>
    <td><code>width</code>
    <td>...
   <tr>
    <td><code>height</code>
    <td>...
   <tr>
    <td><code>device-width</code>
    <td>...
   <tr>
    <td><code>device-height</code>
    <td>...
   <tr>
    <td><code>orientation</code>
    <td>
     <p>If the value is `<code>portrait</code>`: "<code>portrait</code>".</p>
     <p>If the value is `<code>landscape</code>`: "<code>landscape</code>".</p>
   <tr>
    <td><code>aspect-ratio</code>
    <td>...
   <tr>
    <td><code>device-aspect-ratio</code>
    <td>...
   <tr>
    <td><code>color</code>
    <td>...
   <tr>
    <td><code>color-index</code>
    <td>...
   <tr>
    <td><code>monochrome</code>
    <td>...
   <tr>
    <td><code>resolution</code>
    <td>...
   <tr>
    <td><code>scan</code>
    <td>
     <p>If the value is `<code>progressive</code>`: "<code>progressive</code>".</p>
     <p>If the value is `<code>interlace</code>`: "<code>interlace</code>".</p>
   <tr>
    <td><code>grid</code>
    <td>...
  </table>

  <p>Other specifications can extend this table and vendor-prefixed media
  features can have custom serialization formats as well.</p>

  <!-- ........................................................................................................................ -->
  <!-- ........................................................................................................................ -->

  <h3 id="comparing-media-queries"><span class="secno">4.3 </span>Comparing Media Queries</h3>

  <p>To
  <dfn id="compare-media-queries">compare media queries</dfn>
  <var>m1</var> and <var>m2</var> means to
  <a href="#serialize-a-media-query" title="serialize a media query">serialize</a> them both and
  return true if they are a
  <a class="external" href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#case-sensitive">case-sensitive</a> match and false if they
  are not.</p>

  <!-- ........................................................................................................................ -->
  <!-- ........................................................................................................................ -->

  <h3 id="the-medialist-interface"><span class="secno">4.4 </span>The <code>MediaList</code> Interface</h3>

  <p>An object that implements the <a class="idlType" href="#widl-def-MediaList"><code>MediaList</code></a> interface has an associated <dfn id="collection-of-media-queries">collection of media queries</dfn>.</p>
<pre class="idl"><span class="idlInterface" id="widl-def-MediaList">[Constructor]
interface <span class="idlInterfaceID">MediaList</span> {
<span class="idlAttribute">    stringifier attribute <span class="idlAttrType"><a>DOMString</a></span> <span class="idlAttrName"><a href="#widl-MediaList-mediaText">mediaText</a></span>;</span>
<span class="idlAttribute">    readonly attribute <span class="idlAttrType"><a>unsigned long</a></span> <span class="idlAttrName"><a href="#widl-MediaList-length">length</a></span>;</span>
<span class="idlMethod">    <span class="idlMethType"><a>DOMString</a></span> <span class="idlMethName"><a href="#widl-MediaList-item-DOMString-unsigned-long-index">item</a></span> (<span class="idlParam"><span class="idlParamType"><a>unsigned long</a></span> <span class="idlParamName">index</span></span>);</span>
<span class="idlMethod">    <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-MediaList-appendMedium-void-DOMString-medium">appendMedium</a></span> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">medium</span></span>);</span>
<span class="idlMethod">    <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-MediaList-deleteMedium-void-DOMString-medium">deleteMedium</a></span> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">medium</span></span>);</span>
};</span></pre>
<dl class="constructors">
<dt class="constructor" id="widl-MediaList-void">
<code>MediaList</code> ()</dt>
<dd>
<p>To <dfn id="create-a-medialist-object">create a <code>MediaList</code> object</dfn> from a string <var>s</var>, run these steps:</p>   <ol>    <li><p>Create a new <code>MediaList</code> object.</li>    <li><p>Set its <span title="dom-MediaList-mediaText">mediaText</span> attribute to <var>s</var>.</li>    <li><p>Return the newly created <code><code>MediaList</code></code> object.</li>   </ol></dd>
</dl>
<dl class="attributes">
<dt class="attribute" id="widl-MediaList-mediaText">
<code>mediaText</code> of type <span class="idlAttrType"><a>DOMString</a></span></dt>
<dd>
<p>The <code>mediaText</code> attribute must return a <a href="#serialize-a-media-query-list" title="serialize a media query list">serialization</a>   of the <a href="#collection-of-media-queries">collection of media queries</a>.</p>   <p>Setting the <code>mediaText</code> attribute must run these steps:   <ol>    <li><p>Empty the <a href="#collection-of-media-queries">collection of media queries</a>.</li>    <li><p>If the given value is the empty string terminate these steps.</li>    <li><p>Append all the media queries as a result of <a href="#parse-a-media-query-list" title="parse a media query list">parsing</a> the given    value to the <a href="#collection-of-media-queries">collection of media queries</a>.</li>   </ol></dd>
<dt class="attribute" id="widl-MediaList-length">
<code>length</code> of type <span class="idlAttrType"><a>unsigned long</a></span>, readonly</dt>
<dd>
<p>The <code>length</code> attribute must return the number of media queries in the <a href="#collection-of-media-queries">collection of media queries</a>.</dd>
</dl>
<dl class="methods">
<dt class="method" id="widl-MediaList-item-DOMString-unsigned-long-index">
<code>item</code> (<span class="idlParam"><span class="idlParamType"><a>unsigned long</a></span></span>), returns <span class="idlMethType"><a>DOMString</a></span></dt>
<dd>
<p>The <code>item</code> method must return the media query in the <a href="#collection-of-media-queries">collection of media queries</a> given by   <var>index</var>, or null, if <var>index</var> is greater than or equal to the number of media queries in the   <a href="#collection-of-media-queries">collection of media queries</a>.</dd>
<dt class="method" id="widl-MediaList-appendMedium-void-DOMString-medium">
<code>appendMedium</code> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span></span>), returns <span class="idlMethType"><a>void</a></span></dt>
<dd>
<p>The <code>appendMedium</code> method must run these steps:</p>   <ol>    <li><p>Let <var>m</var> be the result of <a href="#parse-a-media-query" title="parse a media query">parsing</a> the given value.</li>    <li><p>If <var>m</var> is null terminate these steps.</li>    <li><p>If <a href="#compare-media-queries" title="compare media queries">comparing</a> <var>m</var> with any of the media queries in the    <a href="#collection-of-media-queries">collection of media queries</a> returns true terminate these steps.</li>    <li><p>Append <var>m</var> to the <a href="#collection-of-media-queries">collection of media queries</a>.</li>   </ol></dd>
<dt class="method" id="widl-MediaList-deleteMedium-void-DOMString-medium">
<code>deleteMedium</code> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span></span>), returns <span class="idlMethType"><a>void</a></span></dt>
<dd>
<p>The <code>deleteMedium</code> method must run these steps:</p>   <ol>    <li><p>Let <var>m</var> be the result of <a href="#parse-a-media-query" title="parse a media query">parsing</a> the given value.</li>    <li><p>If <var>m</var> is null terminate these steps.</li>    <li><p>Remove any media query from the <a href="#collection-of-media-queries">collection of media queries</a> for which    <a href="#compare-media-queries" title="compare media queries">comparing</a> the media query with <var>m</var> returns true.</li>   </ol></dd>
</dl>


  <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

  <h2 id="selectors"><span class="secno">5 </span>Selectors</h2>

  <p>Selectors are defined in the Selectors specification. This section
  mainly defines how to serialize them.</p> <!-- XXX ref -->

  <!-- XXX ref universal selector etc? some are in <span> some not -->

  <!-- ........................................................................................................................ -->
  <!-- ........................................................................................................................ -->

  <h3 id="parsing-selectors"><span class="secno">5.1 </span>Parsing Selectors</h3>

  <p>To
  <dfn id="parse-a-group-of-selectors">parse a group of selectors</dfn>
  means to parse the value using the <code>selectors_group</code>
  production defined in the Selectors specification and return either a
  group of selectors if parsing did not fail or null if parsing did
  fail.</p> <!-- XXX ref -->

  <!-- ........................................................................................................................ -->
  <!-- ........................................................................................................................ -->

  <h3 id="serializing-selectors"><span class="secno">5.2 </span>Serializing Selectors</h3>
  <!-- http://dump.testsuite.org/2009/cssom/serializing-selectors.htm -->

  <p>To
  <dfn id="serialize-a-group-of-selectors">serialize a group of selectors</dfn>
  <a href="#serialize-a-selector" title="serialize a selector">serialize</a> each selector in the
  group of selectors and then
  <a href="#serialize-a-comma-separated-list" title="serialize a comma-separated list">serialize</a> the
  group.</p>

  <p>To <dfn id="serialize-a-selector">serialize a selector</dfn> let
  <var>s</var> be the empty string, run the steps below for each
  part of the chain of the selector, and finally return
  <var>s</var>:</p>

  <ol>
   <li><p>If there is only one <span>simple selector</span> in the
   <span>sequence of simple selectors</span> which is a
   <span>universal selector</span>, append the result of
   <span>universal selector</span> to <var>s</var>.</li>

   <li><p>Otherwise, for each <span>simple selector</span> in the
   <span>sequence of simple selectors</span> that is not a
   universal selector of which the <span>namespace prefix</span> maps to
   the null namespace (not in a namespace) or of which the
   <span>namespace prefix</span> maps to a namespace that is not the
   <span>default namespace</span>
   <a href="#serialize-a-simple-selector" title="serialize a simple selector">serialize</a> the
   <span>simple selector</span> and append the result to
   <var>s</var>.</li>

   <li><p>If this is not the last part of the chain of the selector append a
   space (U+0020), followed by the combinator
   "<code>&gt;</code>",
   "<code>+</code>", or
   "<code>~</code>"
   as appropriate, followed by another space (U+0020) if the combinator was
   not whitespace, to <var>s</var>.</li>

   <li><p>If this is the last part of the chain of the selector and there is
   a pseudo-element, append "<code>::</code>" followed by the name of the
   pseudo-class, to <var>s</var>.</li>
  </ol>


  <p>To
  <dfn id="serialize-a-simple-selector">serialize a simple selector</dfn>
  let <var>s</var> be the empty string, run the steps below, and
  finally return <var>s</var>:</p>

  <dl class="switch">
   <dt>type selector</dt>
   <dt>universal selector</dt>
   <dd>
    <ol>
     <li><p>If the <span>namespace prefix</span> maps to a namespace that is
     not the <span>default namespace</span> and is not the
     null namespace (not in a namespace) append the
     <a href="#serialize-an-identifier" title="serialize an identifier">escaped</a>
     <span>namespace prefix</span>, followed by a "<code>|</code>" (U+007C)
     to <var>s</var>.</li>

     <li><p>If the <span>namespace prefix</span> maps to a namespace that is
     the null namespace (not in a namespace) append
     "<code>|</code>" (U+007C) to <var>s</var>.</li>
     <!-- This includes |* -->

     <li><p>If this is a type selector append the
     <a href="#serialize-an-identifier" title="serialize an identifier">escaped</a> element name to
     <var>s</var>.</li>

     <li><p>If this is a universal selector append "<code>*</code>" (U+002A)
     to <var>s</var>.</li>
    </ol>
   </dd>

   <dt>attribute selector</dt>
   <dd>
    <ol>
     <li><p>Append "<code>[</code>" (U+005B) to
     <var>s</var>.</li>

     <li><p>If the <span>namespace prefix</span> maps to a namespace that is
     not the null namespace (not in a namespace) append the
     <a href="#serialize-an-identifier" title="serialize an identifier">escaped</a>
     <span>namespace prefix</span>, followed by a "<code>|</code>" (U+007C)
     to <var>s</var>.</li>

     <li><p>If the <span>namespace prefix</span> maps to a namespace that is
     the null namespace (not in a namespace) append
     "<code>|</code>" (U+007C) to <var>s</var>.</li>
     <!-- This includes |* -->

     <li><p>Append the <a href="#serialize-an-identifier" title="serialize an identifier">escaped</a>
     attribute name to <var>s</var>.</li>

     <li><p>If there is an attribute value specified, append
     "<code>=</code>",
     "<code>~=</code>",
     "<code>|=</code>",
     "<code>^=</code>",
     "<code>$=</code>", or
     "<code>*=</code>"
     as appropriate (depending on the type of attribute selector), followed
     by the <a href="#serialize-a-string" title="serialize a string">string escaped</a>
     attribute value, to <var>s</var>.</li>

     <li><p>Append "<code>]</code>" (U+005D) to
     <var>s</var>.</li>
    </ol>
   </dd>

   <dt>class selector</dt>
   <dd><p>Append a "<code>.</code>" (U+002E), followed by the
   <a href="#serialize-an-identifier" title="serialize an identifier">escaped</a> class name to
 
A364
  <var>s</var>.</dd>

   <dt>ID selector</dt>
   <dd><p>Append a "<code>#</code>" (U+0023), followed by the
   <a href="#serialize-an-identifier" title="serialize an identifier">escaped</a> ID to
   <var>s</var>.</dd>

   <dt>pseudo-class</dt>
   <dd>
    <p>If the pseudo-class does not accept arguments append
    "<code>:</code>" (U+003A), followed by the name of the pseudo-class, to
    <var>s</var>.</p>

    <p>Otherwise, append "<code>:</code>" (U+003A), followed by the name of
    the pseudo-class, followed by "<code>(</code>" (U+0028), followed by the
    value of the pseudo-class argument determined as per below, followed by
    "<code>)</code>" (U+0029), to <var>s</var>.</p>

    <dl class="switch">
     <dt><code>:lang()</code></dt>
     <dd><p>The <a href="#serialize-an-identifier" title="serialize an identifier">escaped</a>
     value.</dd>

     <dt><code>:nth-child()</code></dt>
     <dt><code>:nth-last-child()</code></dt>
     <dt><code>:nth-of-type()</code></dt>
     <dt><code>:nth-last-of-type()</code></dt>
     <dd>
      <ol>
       <li><p>If the value is odd let the value be
       "<code>2n+1</code>".</li>

       <li><p>If the value is even let the value be
       "<code>2n</code>".</li>

       <li><p>If <var>a</var> is zero let the value be
       <var>b</var>
       <a href="#serialize-a-css-value-component" title="serialize a CSS component value">serialized</a> as &lt;integer&gt;.</li>

       <li><p>If <var>a</var> is one or minus one and
       <var>b</var> is zero let the value be
       "<code>n</code>" (U+006E).</li>

       <li><p>If <var>a</var> is one or minus one let the value be
       "<code>n</code>" (U+006E), followed by
       "<code>+</code>" (U+002B) if <var>b</var> is positive,
       followed by <var>b</var>
       <a href="#serialize-a-css-value-component" title="serialize a CSS component value">serialized</a> as &lt;integer&gt;.</li>

       <li><p>If <var>b</var> is zero let the value be
       <var>a</var>
       <a href="#serialize-a-css-value-component" title="serialize a CSS component value">serialized</a> as &lt;integer&gt;,
       followed by "<code>n</code>" (U+006E).</li>

       <li><p>Otherwise let the value be
       <var>a</var>
       <a href="#serialize-a-css-value-component" title="serialize a CSS component value">serialized</a> as &lt;integer&gt;,
       followed by "<code>n</code>" (U+006E), followed by
       "<code>+</code>" (U+002B) if <var>b</var> is positive,
       followed by <var>b</var>
       <a href="#serialize-a-css-value-component" title="serialize a CSS component value">serialized</a> as &lt;integer&gt;.</li>
      </ol>
     </dd>

     <dt><code>:not()</code></dt>
     <dd><p>The result of serializing the value using the rules for
     <a href="#serialize-a-group-of-selectors" title="serialize a group of selectors">serializing a group of selectors</a>.</dd>
    </dl>
   </dd>
  </dl>

  <!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->

  <h2 id="css"><span class="secno">6 </span>CSS</h2>

  <!-- ........................................................................................................................ -->
  <!-- ........................................................................................................................ -->

  <h3 id="style-sheet-0"><span class="secno">6.1 </span>Style Sheet</h3>

  <!-- XXX
   element inserted into the DOM, style sheet created, element removed from
   the DOM, what happens to StyleSheet?
  -->

  <p>A <dfn id="style-sheet">style sheet</dfn> is an abstract concept that
  represents a style sheet as defined by the CSS specification. In the DOM a
  <a href="#style-sheet">style sheet</a> is a <code>CSSStyleSheet</code> object. A
  <a href="#style-sheet">style sheet</a> has a number of associated properties:</p>

  <dl>
   <dt><dfn id="style-sheet-type">style sheet type</dfn></dt>
   <dd><p>The literal string "<code>text/css</code>".</dd>

   <dt><dfn id="style-sheet-location">style sheet location</dfn></dt>
   <dd><p>The <a class="external" href="http://www.whatwg.org/specs/web-apps/current-work/multipage/urls.html#url">URL</a> of the
   <a href="#style-sheet">style sheet</a> or null if the <a href="#style-sheet">style sheet</a> was
   embedded.</dd>

   <dt><dfn id="style-sheet-parent">style sheet parent</dfn></dt>
   <dd><p>The <a href="#style-sheet">style sheet</a> that is the parent of the
   <a href="#style-sheet">style sheet</a>.</dd>

   <dt><dfn id="style-sheet-owner-node">style sheet owner node</dfn></dt>
   <dd><p>The DOM node associated with the <a href="#style-sheet">style sheet</a> or
   null if there is no associated DOM node.</dd>

   <dt><dfn id="style-sheet-owner-css-rule">style sheet owner CSS rule</dfn></dt>
   <dd><p>The <span>CSS rule</span> in the <a href="#style-sheet-parent">style sheet parent</a>
   that caused the inclusion of the <a href="#style-sheet">style sheet</a> or null if
   there is no such <span>CSS rule</span>.</dd>

   <dt><dfn id="style-sheet-media">style sheet media</dfn></dt>
   <dd>
    <p>The <code>MediaList</code> object associated with the
    <a href="#style-sheet">style sheet</a>.</p>

    <p>If this property is set to a string run the
    <a href="#create-a-medialist-object">create a <code>MediaList</code> object</a> steps for that
    string and associate the returned object with the
    <a href="#style-sheet">style sheet</a>.</p>
   </dd>

   <dt><dfn id="style-sheet-title">style sheet title</dfn></dt>
   <dd>
    <p>The title of the <a href="#style-sheet">style sheet</a>. It is said to be empty
    if the title is the empty string.</p>

    <div class="example">
     <p>In these examples the <a href="#style-sheet-title">style sheet title</a> ends up being
     empty:</p>

     <pre>&lt;style&gt; body { background:papayawhip } &lt;/style&gt;</pre>

     <pre>&lt;style&gt; body { background:orange } &lt;/style&gt;</pre>
    </div>
   </dd>

   <dt><dfn id="style-sheet-alternate-flag">style sheet alternate flag</dfn></dt>
   <dd>
    <p>Either set or unset. Unset by default.</p>

    <div class="example">
     <p>The following <a href="#style-sheet" title="style sheet">style sheets</a> have
     their <a href="#style-sheet-alternate-flag">style sheet alternate flag</a> set:</p>

     <pre><code>&lt;?xml-stylesheet alternate="yes" title="x" href="data:text/css,…"?&gt;</code></pre>

     <pre
685C
><code>&lt;link rel="alternate stylesheet" title="x" href="data:text/css,…"&gt;</code></pre>
    </div>
   </dd>

   <dt><dfn id="style-sheet-disabled-flag">style sheet disabled flag</dfn></dt>
   <dd>
    <p>Either set or unset. Unset by default.</p>

    <p class="note">Even when unset it does not necessarily mean that the
    <a href="#style-sheet">style sheet</a> is actually used for rendering.</p>
   </dd>


   <dt><dfn id="style-sheet-css-rules">style sheet CSS rules</dfn></dt>
   <dd><p>The <span title="CSS rule">CSS rules</span> associated with the
   <a href="#style-sheet">style sheet</a>.</dd>
  </dl>

  <p>When you are to <a href="#create-a-style-sheet">create a style sheet</a> the above properties,
  with the exception of <a href="#style-sheet-type">style sheet type</a> and
  <a href="#style-sheet-css-rules">style sheet CSS rules</a>, are to be set to
  their proper values.</p>

  <!-- same-origin restrictions -->

  <!-- ........................................................................................................................ -->

  <h4 id="the-stylesheet-interface"><span class="secno">6.1.1 </span>The <code>StyleSheet</code> Interface</h4>

  <p>The <code>StyleSheet</code> interface represents an abstract, base style sheet.</p>
<pre class="idl"><span class="idlInterface" id="widl-def-StyleSheet">interface <span class="idlInterfaceID">StyleSheet</span> {
<span class="idlAttribute">    readonly attribute <span class="idlAttrType"><a>DOMString</a></span> <span class="idlAttrName"><a href="#widl-StyleSheet-type">type</a></span>;</span>
<span class="idlAttribute">    readonly attribute <span class="idlAttrType"><a>DOMString</a>?</span> <span class="idlAttrName"><a href="#widl-StyleSheet-href">href</a></span>;</span>
<span class="idlAttribute">    readonly attribute <span class="idlAttrType"><a>Node</a></span> <span class="idlAttrName"><a href="#widl-StyleSheet-ownerNode">ownerNode</a></span>;</span>
<span class="idlAttribute">    readonly attribute <span class="idlAttrType"><a>StyleSheet</a>?</span> <span class="idlAttrName"><a href="#widl-StyleSheet-parentStyleSheet">parentStyleSheet</a></span>;</span>
<span class="idlAttribute">    readonly attribute <span class="idlAttrType"><a>DOMString</a>?</span> <span class="idlAttrName"><a href="#widl-StyleSheet-title">title</a></span>;</span>
<span class="idlAttribute">    readonly attribute <span class="idlAttrType"><a>MediaList</a></span> <span class="idlAttrName"><a href="#widl-StyleSheet-media">media</a></span>;</span>
<span class="idlAttribute">    attribute <span class="idlAttrType"><a>boolean</a></span> <span class="idlAttrName"><a href="#widl-StyleSheet-disabled">disabled</a></span>;</span>
};</span></pre>
<dl class="attributes">
<dt class="attribute" id="widl-StyleSheet-type">
<code>type</code> of type <span class="idlAttrType"><a>DOMString</a></span>, readonly</dt>
<dd>
<p>The <code>type</code> attribute must return the <a href="#style-sheet-type">style sheet type</a>.</dd>
<dt class="attribute" id="widl-StyleSheet-href">
<code>href</code> of type <span class="idlAttrType"><a>DOMString</a></span>, readonly</dt>
<dd>
<p>The <code>href</code> attribute must return the <a href="#style-sheet-location">style sheet location</a> or null if none.</p>    <p class="issue">What should the default value be if not known or specified upon creation? an empty string or null?</dd>
<dt class="attribute" id="widl-StyleSheet-ownerNode">
<code>ownerNode</code> of type <span class="idlAttrType"><a>Node</a></span>, readonly</dt>
<dd>
<p>The <code>ownerNode</code> attribute must return the <a href="#style-sheet-owner-node">style sheet owner node</a>.</p>    <p class="issue">Should <code>ownerNode</code> be nullable?</dd>
<dt class="attribute" id="widl-StyleSheet-parentStyleSheet">
<code>parentStyleSheet</code> of type <span class="idlAttrType"><a>StyleSheet</a></span>, readonly</dt>
<dd>
<p>The <code>parentStyleSheet</code> attribute must return the <a href="#style-sheet-parent">style sheet parent</a> or null if there is none.</dd>
<dt class="attribute" id="widl-StyleSheet-title">
<code>title</code> of type <span class="idlAttrType"><a>DOMString</a></span>, readonly</dt>
<dd>
<p>The <code>title</code> attribute must return the <a href="#style-sheet-title">style sheet title</a> or null if none.</p>    <p class="issue">What should the default value be if not known or specified upon creation? an empty string or null?</dd>
<dt class="attribute" id="widl-StyleSheet-media">
<code>media</code> of type <span class="idlAttrType"><a>MediaList</a></span>, readonly</dt>
<dd>
<p>The <code>media</code> attribute must return the <a href="#style-sheet-media">style sheet media</a>.</p>    <p class="issue">Should <code>media</code> be nullable?</p>    <p class="issue">Need to define a setter that implements the semantics of setting this attribute to a string representing a MediaList.</dd>
<dt class="attribute" id="widl-StyleSheet-disabled">
<code>disabled</code> of type <span class="idlAttrType"><a>boolean</a></span></dt>
<dd>
<p>The <code>disabled</code> attribute must return true if the <a href="#style-sheet-disabled-flag">style sheet disabled flag</a>    is set, or false otherwise.</p>    <p>Setting the <code>disabled</code> attribute must set the <a href="#style-sheet-disabled-flag">style sheet disabled flag</a>    if the new value is true, or unset the <a href="#style-sheet-disabled-flag">style sheet disabled flag</a> otherwise.</dd>
</dl>


  <!-- ........................................................................................................................ -->

  <h4 id="the-cssstylesheet-interface"><span class="secno">6.1.2 </span>The <code>CSSStyleSheet</code> Interface</h4>

  <p>The <code>CSSStyleSheet</code> interface represents a CSS <a href="#style-sheet">style sheet</a> rule.</p>
<pre class="idl"><span class="idlInterface" id="widl-def-CSSStyleSheet">interface <span class="idlInterfaceID">CSSStyleSheet</span> : <span class="idlSuperclass"><a class="idlType" href="#widl-def-StyleSheet"><code>StyleSheet</code></a></span> {
<span class="idlAttribute">    readonly attribute <span class="idlAttrType"><a>CSSRule</a>?</span> <span class="idlAttrName"><a href="#widl-CSSStyleSheet-ownerRule">ownerRule</a></span>;</span>
<span class="idlAttribute">    readonly attribute <span class="idlAttrType"><a>CSSRuleList</a></span> <span class="idlAttrName"><a href="#widl-CSSStyleSheet-cssRules">cssRules</a></span>;</span>
<span class="idlMethod">    <span class="idlMethType"><a>unsigned long</a></span> <span class="idlMethName"><a href="#widl-CSSStyleSheet-insertRule-unsigned-long-DOMString-rule-unsigned-long-index">insertRule</a></span> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span> <span class="idlParamName">rule</span></span>, <span class="idlParam"><span class="idlParamType"><a>unsigned long</a></span> <span class="idlParamName">index</span></span>);</span>
<span class="idlMethod">    <span class="idlMethType"><a>void</a></span> <span class="idlMethName"><a href="#widl-CSSStyleSheet-deleteRule-void-unsigned-long-index">deleteRule</a></span> (<span class="idlParam"><span class="idlParamType"><a>unsigned long</a></span> <span class="idlParamName">index</span></span>);</span>
};</span></pre>
<dl class="attributes">
<dt class="attribute" id="widl-CSSStyleSheet-ownerRule">
<code>ownerRule</code> of type <span class="idlAttrType"><a>CSSRule</a></span>, readonly</dt>
<dd>
<p>The <code>ownerRule</code> attribute must return the <a href="#style-sheet-owner-css-rule">style sheet owner CSS rule</a> or null if none.</dd>
<dt class="attribute" id="widl-CSSStyleSheet-cssRules">
<code>cssRules</code> of type <span class="idlAttrType"><a>CSSRuleList</a></span>, readonly</dt>
<dd>
<p>The <code>cssRules</code> attribute must return a <code>CSSRuleList</code> object representing the <a href="#style-sheet-css-rules">style    sheet CSS rules</a>.</p>    <p class="note">CSS rules that were dropped during parsing can not be    found using APIs described by this specification.</dd>
</dl>
<dl class="methods">
<dt class="method" id="widl-CSSStyleSheet-insertRule-unsigned-long-DOMString-rule-unsigned-long-index">
<code>insertRule</code> (<span class="idlParam"><span class="idlParamType"><a>DOMString</a></span></span>, <span class="idlParam"><s
62F3
pan class="idlParamType"><a>unsigned long</a></span></span>), returns <span class="idlMethType"><a>unsigned long</a></span></dt>
<dd>
<p>The <code>insertRule</code> operation must <a href="#insert-a-css-rule">insert a CSS rule</a> <var>rule</var> the in CSS rule    list returned by <code title="dom-CSSStyleSheet-cssRules">cssRules</code> at    <var>index</var>.</dd>
<dt class="method" id="widl-CSSStyleSheet-deleteRule-void-unsigned-long-index">
<code>deleteRule</code> (<span class="idlParam"><span class="idlParamType"><a>unsigned long</a></span></span>), returns <span class="idlMethType"><a>void</a></span></dt>
<dd>
<p>The <code>deleteRule</code> operation must <a href="#remove-a-css-rule">remove a CSS rule</a> from the CSS rule list returned by    <code title="dom-CSSStyleSheet-cssRules">cssRules</code> at <var>index</var>.</dd>
</dl>


  <!-- ........................................................................................................................ -->
  <!-- ........................................................................................................................ -->

  <h3 id="style-sheet-collections"><span class="secno">6.2 </span>Style Sheet Collections</h3>

  <p>Below various new concepts are defined that are associated with each
  <code class="external"><a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#document">Document</a></code> object.</p>

  <p>Each <code class="external"><a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#document">Document</a></code> has an associated list of zero or more
  <a href="#style-sheet" title="style sheet">style sheets</a>, named the
  <dfn id="document-style-sheets">document style sheets</dfn>. This is
  an ordered list that contains all
  <a href="#style-sheet" title="style sheet">style sheets</a> associated with the
  <code class="external"><a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#document">Document</a></code>, in
  <a class="external" href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#concept-tree-order" title="concept-tree-order">tree order</a>, with
  <a href="#style-sheet" title="style sheet">style sheets</a> created from HTTP
  <code title="http-link">Link</code> headers first, if any, in header
  order.</p>

  <p>To <dfn id="create-a-style-sheet">create a style sheet</dfn>, run these
  steps:</p>

  <ol>
   <li><p>Create a new <a href="#style-sheet">style sheet</a> object and set its
   properties as specified.</li>

   <li><p>Then run the <a href="#add-a-style-sheet">add a style sheet</a> steps for the newly
   created <a href="#style-sheet">style sheet</a>.</li>
  </ol>

  <p>To <dfn id="add-a-style-sheet">add a style sheet</dfn>, run these
  steps:</p>

  <ol>