Interactivity
Provide an accessible alternate when using a nonstandard format

Not everything that appears on a Web page is essential to the user experience. For example, users do not necessarily need access to JavaScript rollovers to access the content of a Web site. The fact that an image highlights when rolled over by the mouse is not a functional necessity. Such rollover effects are generally used to provide visual interest, or to draw attention to functional elements such as links—not for essential site content. On the other hand, when site navigation is provided using Flash, users who do not have Flash installed, or who have difficultly accessing Flash-based content, will be unable to access the Web site (Figure 13.5).

Figure 13.5: Sites that use Flash exclusively for content and navigation (1) must provide an HTML alternative (2). Otherwise, users who cannot access Flash will be unable to use the site. nces.ed.gov/nceskids

Whenever providing essential functionality in a format that may be inaccessible to some users, provide the equivalent information as accessible HTML text (Figure 13.6). For example, when using Flash for navigation, provide alternate HTML text links for users who cannot access Flash. When using JavaScript for essential content, use the NOSCRIPT tag to provide equivalent content for users who cannot access JavaScript.

Figure 13.6: Nova offers users the choice (1) of viewing Approximating Pi in Flash format (2) or as HTML text and images (3). www.pbs.org/wgbh/nova/archimedes