HTML and CSS Reference
■ Duplicated attributes on the same element might cause key errors for assistive technology and must be
The appearance of elements receiving focus or being hovered over with a pointing device should be changed
(for example, highlighted) to provide visual feedback to the user (such as changed background or border color). Flash
content should also provide highly visible focus indication.
Alternate texts, labels, and names should be shared among components with the same functionality.
An optional sign language version provided for all information required to use the content can improve
accessibility for people who are deaf or have cognitive disabilities. It can be either a multimedia avatar using a
technology such as Flash or a video clip of an animated or real sign language interpreter (Figure 10-9 ).
Figure 10-9. A signing avatar 
Web site components such as markup, style sheets, and XML files must be validated to guarantee the proper use
of formal specifications, grammar, syntax, and vocabulary. Opening and closing tags must be used according to the
markup specification. All web pages must be well-formed.