HTML and CSS Reference
In-Depth Information
U.S. Section 508
Beyond W3C standards, there are country-specific standards and/or legislations on web accessibility around the
world. In the United States, a basic requirement for government web sites is Section 508 compliance. Subpart B of
the Amendment describes technical standards. The most important part for web developers is §1194.22 (Web-based
Intranet and Internet Information and Applications) [44].
The web-based technology and information criteria defined by Section 508 are based on W3C WAI guidelines.
Consequently, §1194.22 and WCAG 1.0 checkpoints are consistent [45].
There are no limitations on graphic or animation use, but they must be provided in an accessible form. Beyond
the text labels and descriptions provided for graphics, this section also addresses usability of style sheets, forms,
scripting, multimedia contents, image maps, languages, and plugins.
An alternate text should be written for all nontext elements. Multimedia presentations should be synchronized
with their equivalent alternatives. Information cannot be expressed in color alone.
Information representation cannot rely exclusively on associated style sheets.
Row and column headers should be declared for data tables.
Data cells and header cells of data tables should be associated.
Client-side image maps should be preferred to server-side image maps except where the regions cannot be
defined with an available geometric shape.
Redundant text links should be provided for all active regions of server-side image maps.
Frames should have unique titles.
Screen flickering with a frequency of 2-55 Hz should be eliminated.
A text-only page should be provided with equivalent information and functionality.
Assistive technology must be able to access content generated by scripting.
Web content that requires third-party software such as plug-ins must provide a link to the plug-in web site.
Forms should be accessible for assistive technology.
Users should be allowed to skip repetitive navigation links.
Users should be notified on timed response requirements and allowed to extend time limits.
Semantic (X)HTML5 Elements and WAI-ARIA
The new semantic markup elements introduced in the HTML5 specification such as header , footer , article ,
section , aside , and nav involve accessibility potential.
The support for ARIA roles is also increasing. ARIA roles can be applied as additional markup to improve
accessibility potential; in other words, their presence does not cause any problems on systems without ARIA support.
ARIA roles are added as attributes to elements such as banner , complementary , contentinfo , form , main , navigation ,
or search . Several ARIA roles describe document structure, namely, article , columnheader , definition , directory ,
document , group , heading , img , list , listitem , math , note , presentation , region , row , rowheader , separator , and
toolbar .
The role of structuring elements can be provided by the role attribute. Listing 10-14 shows an example.
Listing 10-14. Using the role Attribute
<header role="banner" />
Certain roles must be unique within a page. The banner header code shown is a good example. While developers
can use an unlimited number of headers, only one header can be a banner header.
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