• Section 508 defines 16 accessibility requirements to which Web sites must comply.
• Many Web Designers confuse Section 508 requirements with the much broader and stricter W3C accessibility requirements.
• Section 508 is a simpler set of accessibility requirements that do not require radical changes to the structure of your Web pages.
• Section 508 may require Web sites to significantly change their use of Flash and Dynamic HTML.

Federal regulations require government Web sites to be accessible to people with disabilities. However, defining exactly what this means has been a point of confusion in the past.

Previous government regulations have directed Web sites to be accessible, without specifying exactly what steps are necessary to accomplish this. Section 508 represents the first time the government has explicitly defined what it means to be accessible. As a result, many experts believe that Section 508 will become the standard for Web accessibility in both the government and commercial sectors.

However, Section 508 is not the only Web accessibility standard in existence. In particular, many Web Designers confuse Section 508 requirements with the World Wide Web Consortium's (W3C) older Web Accessibility Initiative (WAI) guidelines.

While eleven of the sixteen Section 508 requirements are based on WAI guidelines, Section 508 represents a lighter, simpler approach to Web Accessibility. Full implementation of the WAI guidelines requires Web sites to undergo radical surgery. For example, the WAI guidelines call for Web Designers to abandon the use of tables to control layout, and to separate the structure and content of their page through the extensive use of Cascading Style Sheets. Full compliance with all Priority 1-3 WAI guidelines would require many Web sites to be rebuilt from the ground up.

Note that many Web accessibility testing tools are not focused specifically on Section 508. As a result they may point users toward implementing WAI guidelines that aren't required for Section 508 compliance.

Section 508 requirements allow accessibility support to be added to a Web page without changing the underlying layout of a Web page. However, Section 508 requires all technologies used on a Web page to be fully accessible. This may cause problems for sites that use Flash or Dynamic HTML (see paragraphs B, D and L below for details).

The following paragraphs list each Section 508 requirement and explain what it means for Web Designers.

Many visually impaired people use screen readers such as JAWS that speak the text found on your Web page. If critical information on your page is presented inside graphics, multimedia objects, applets, or plug-ins, screen readers may not be able to speak the information.

This requirement calls on Web Designers to include text alternatives for each such object found on their page. For example, all images are expected to have an ALT attribute that describes the image, and scripts that create page content are expected to have NOSCRIPT alternatives.

To support disabled users, Web Designers should ideally use multimedia formats that support synchronized captioning. Currently only QuickTime, SMIL, and SAMI support this. Flash is notable in not supporting synchronized captions.

Under some interpretations of this requirement, it is sufficient to provide disabled visitors with a text transcript or other alternative that presents the same information found in the multimedia. Thus some Flash designers export their presentation as HTML and point disabled visitors to this.

While Web Designers often balk at this requirement, colorblind visitors represent the largest segment of the disabled population, with over 7 million Americans being affected. Between 5-7% of Caucasian males are affected by some form of color blindness.

This requirement calls on Web Designers to view their pages with color removed to make sure that critical information is not lost. For example, a Web form that states "required fields are shown in red" would not meet this requirement.

Cascading Style Sheets can both help and hurt accessibility. On the plus side, disabled users can define their own custom Style Sheets that override the page styles defined by a Web site. This allows a visually impaired user to set page fonts to be larger, and change text and background colors to provide higher contrast.

On the negative side, Style Sheets are sometimes used to affect the content displayed on a page. They can be used to hide, show, or position page content. This is true with Dynamic HTML scripts that create scrolling text or drop-down navigation menus.

This use of Style Sheets presents a problem for the disabled, because many disabled visitors use older, special purpose browsers that do not understand Style Sheets. If one of these users visits a site using DHTML drop-down menus, they may not be able to navigate its pages.

Of course, the disabled user could simply upgrade to a newer browser. But special purpose browsers and assistive technologies are expensive (JAWS costs $600), and many of the disabled live on a limited income.

This requirement is unlikely to affect many Web Designers, since server-side image maps are rarely used today. In addition, in nearly all cases a client-side image map can accomplish the same task as a server-side map.

Client-side image maps are preferred over server-side maps, because each hot spot on the image map can have its own ALT attribute. Thus screen reader will be able to explain each spot.

This requirement applies only to data tables, not to tables used to control page layout. If a table is used to show information, such as the average temperature in different cities, then it must be properly labeled.

Proper labeling allows screen readers to speak out the row and column labels associated with each table cell. Lacking this information, screen readers can make a data table sound like a confusing list of seemingly random numbers. Proper labeling involves the use of tags including TH, COLGROUP, and CAPTION.

As with the previous paragraph, this requirement applies only to data tables. In addition, it affects only data tables that set ROWSPAN or COLSPAN attributes. Rows or columns that span multiple cells can confuse screen readers if they are not properly labeled.

Pages that use frames must assign a title to each frame. This allows a screen reader to announce the purpose of each frame. For example, JAWS might announce one frame as the "navigation frame" and another as the "content frame." This helps orient visually impaired users.

This requirement poses a formidable challenge for most Web Designers. Since flickering images can cause epileptic seizures, this type of image should be avoided at all costs. However, most Web Designers aren't able to determine if their GIFs cycle at a frequency within the danger range. As a result, this requirement has moved some government agencies to place a blanket ban on all animated graphics.

The content of the text-only page shall be updated whenever the primary page changes. This measure is a last resort to be used only if a page cannot be made accessible in any other means. Text-only pages increase the Webmaster's maintenance load, and may be forgotten when the main Web pages are updated.

This two-part requirement affects both visually impaired users and users with motor skill impairments. The first part of the requirement calls for all scripts that display content to have NOSCRIPT alternatives.

The second part requires that scripts be device-independent. That is to say, a script must be operable with either mouse or keyboard.

This requirement may affect Dynamic HTML scripts that create scrolling text or drop-down menus.

If applets or plug-ins are used on a Web page, they must be accessible. This means that users should be able to operate the applet using either keyboard or mouse, the applet's content must be readable by screen readers, and ideally the user should be able to control the applet's colors and text size.

Form accessibility is an especially challenging area. While the latest versions of HTML provide tags such as LABEL, OPTGROUP, and LEGEND that are designed to help assistive technologies interpret forms, today's browsers and screen readers do not yet support these tags.

As a result, Web Designers need to take special care when positioning text next to form fields. Badly positioned text can lead to a form field being mislabeled by tools like JAWS.

Sighted users experience Web pages in two dimensions, which allows their eyes to move directly to the page's content. Assistive technologies such as JAWS present Web pages in one dimension (that is to say, they linearize the page). If JAWS encounters a navigation bar with 20 links, disabled users must read through every one of these links before being able to access the next part of the page. Even if they use the tab or arrow keys to move from link to link, this is a tedious process.

As a result, this requirement encourages Web Designers to give disabled visitors the option to skip parts of the page that consist only of navigation. This is typically accomplished by using bookmark anchors. Many accessible pages include a hidden GIF at the page top that gives disabled visitors a bookmark link straight to the page's content.

While assistive technologies allow people with disabilities to read Web pages, the speed of the disabled user's interaction with the page is often slower than that of people without disabilities. If the page contains a form requiring a timed response, this can create problems.

This requirement deals specifically with JavaScript or other technology that may cause a page timeout. Some Webmasters have also interpreted this requirement as barring meta-refresh tags.

Further Reading:

• Section 508 Requirements: http://www.section508.gov/final_text.html
• World Wide Web Consortium Web Accessibility Initiative: http://www.w3c.org/WAI/