Validation - Web Standards: Mastering HTML5, CSS3, and XML - page 446

and some of them are incorrect (for example, the lang attribute on the html element is neither valid nor required in
XHTML+RDFa if the natural language of the document is identified by the xml:lang attribute) (Figure 14-7 ).
Figure 14-7. AChecker provides good suggestions; however, not all of them would be valid
AChecker also supports HTML validation. It provides error descriptions and suggestions for corrections.
The online accessibility validation tool Cynthia can perform validations by URI according to Section 508
and WCAG 1.0 with all priority levels [20]. Advanced options are also available such as browser emulation or line
exclusions. Reports are clear and useful for developers dealing with accessibility (Figure 14-8 ).
Figure 14-8. Detailed accessibility report with explanations and links to W3C guidelines
One of the most comprehensive accessibility tools is WebAIM WAVE [21]. It is a free online tool at
http://wave.webaim.org that renders web pages with accessibility errors, warnings, and information (Figure 14-9 ).
It identifies accessible attribute values, inaccessible and potentially inaccessible content such as Flash or scripts, and
device-dependent content such as keyboard traps.