When viewed through a graphical browser such as Netscape Navigator or Internet Explorer, a beautiful picture of a floor map of a library appears. The visitor can choose selected areas of the library to view. When a visitor using a text-based browser visits the site, this is what he sees:
Our Library Page
At this point the visitor is stuck, because text-based browsers will not interpret the hypertext links embedded in the image map. His only option is to back out of the site. A visitor who uses a text-based browser, perhaps because he is blind, can't get to your information unless an alternative is provided. The accessibility of an image map depends on the software used as a Web site's server. Check with your system administrator to find out about the capabilities of your Web server software. Some server software will automatically render text links for image maps while other versions won't. Providing text alternatives to image-based links will ensure image maps are available to the widest audience.
- Include descriptive captions for pictures and transcriptions of manuscript images. Providing ALT text for an image is sufficient for logos and graphics that contain little information content. However, if the graphics provide more extensive information, adding captions and transcriptions is important for those who cannot see your page because they are using a text-based browser or they have turned off the graphics loading feature of their browser. This includes people who are blind. If you are not sure how critical a particular image is to the content of a page, temporarily remove it and consider the impact of its loss. If you present information in an image format, such as a scanned-in image of a page of a manuscript, be sure to also provide a transcription of the manuscript in a straight text format. This alternative is useful for many visitors, including those with visual impairments and those with learning disabilities who may have difficulty reading the original document.
- Use a NULL value for unimportant graphics. Some graphical elements may add no content to a page and can be bypassed from viewing by using an ALT attribute with no text. By using just two quotation marks with no content, you can reduce the amount of distracting text when a page is viewed with graphics capabilities turned off or with a text-based browser. For example, the HTML for a divider bar could be:
Sighted visitors will see the divider bar, while those visiting via a text browser will see/hear nothing.
- Provide audio description and captions or transcripts of video. If your multimedia resources provided on your site include video, people who can not see will be unable to use this information unless it is provided in an alternative format. A synchronized text transcription provided with the video will give a visitor who cannot see, or who doesn't have the appropriate viewing software, access to the information in your video clip. Their screen reader will read aloud the text transcription. It is also important to describe what is happening in the movie for users who may not be able to see what is happening. An alternative to the synchronized text track would be a transcript of the video providing both descriptions of what is happening and also the audio transcript.
Captions on a video and transcripts also provide access to the content for those who cannot hear. (Resources for captioning video and audio description for video) Always provide a text version of any stand-alone audio files. If the clip is short, you can place the text in the link or in the alt tag of an image associated with the link. If the file is long, you may want to consider linking to a page that contains the transcript. If you use sounds to enhance a page, provide text to describe the sound. This is especially important if you embed sounds that are played automatically. You should always give the user the ability to turn the sound off.
Apple's QuickTime allows you to provide captions which can be syncronized with the movie. For more information, view Apple's QuickTime and SMIL. The World Wide Web Consortium has developed a standard for syncronizing media used in multimedia files. This standard is known as Synchronized Multimedia Integration Language (SMIL). Many companies have developed products which allow you to develop multimedia for the web. Most of these products produce files that are played using Real Networks G2 player. A list of development tools is provided by Streaming Media World.
- Consider other options for making graphical features accessible. Some Web designers make an image accessible by placing a hyperlink "D" (for description) immediately before or after an image that links to another page with an image description. At the end of each description another hyperlink returns the user to the original page. This method should be used with caution as it can add unnecessary navigational complexity to the site.
Some organizations with graphic-intensive Web pages provide a separate text version of their site to ensure accessibility. This adds maintenance time and complexity because two versions of a site must be updated simultaneously. It also segregates site visitors according to the type of equipment they use to access the Web. As much as possible, design a single version of your site so that it is accessible to all visitors.
- Use tables and frames sparingly and consider alternatives.
Most screen reader programs read from left to right, jumbling the meaning of information in tables. Some blind visitors can interpret tabular information, but it is best to look for other ways to present the information to ensure that visitors with visual impairments can reach your data. In the same vein, frames can be difficult for text-based screen reading software to access. Evaluate whether frames are truly necessary at your site. When frames are used, ensure that frames are labeled with the TITLE attribute, provide a text alternative with NOFRAMES, and use the TARGET = "_top" attribute to ensure useful Uniform Resource Location (URL) addressing is provided for each interior frame.
- Provide alternatives for forms and databases.
Some combinations of browsers and screen readers encounter errors with nonstandard or complex forms. Always test forms and databases with a text-based browser. Include an e-mail address and other contact information for those who cannot use your forms or database.
Web Pages Test
Test your Web site with a variety of Web browsers, and always test your pages with at least one text-based browser and with multi-media browsers with graphics and sound-loading features turned off. This way you will see your Web resources from the many perspectives of your users. Also view the resources at your site using a variety of computer platforms, monitor sizes, and screen resolutions. Make sure you can access all of the features of your web site with the keyboard alone; this test simulates the experience of web users who cannot use a mouse. Make use of accessibility testing software such as A-Prompt, Bobby, and WAVE (see Resources); they will point out elements that could be inaccessible. Revise your HTML to make your site accessible.
ADA accessibility requirements apply to Internet Web pages. (1996). The Law Reporter, 10(6), 1053-1084.
Americans with Disabilities Act of 1990 http://www.usdoj.gov/crt/ada/adahom1.htm
Bobby, CAST (Center for Applied Special Technology) http://www.cast.org/bobby/
DO-IT (Disabilities, Opportunities, Internetworking and Technology) - Accessible Web Page Design http://www.washington.edu/doit/Resources/web-design.html
EASI (Equal Access to Software and Information) http://www.isc.rit.edu/~easi/
International Center for Disability Resources on the Internet http://www.icdri.org/
Java accessibility resources http://www.sun.com/access/
National Center for Accessible Media (NCAM) resources http://ncam.wgbh.org/
Section 508 Standards of the Access Board http://www.access-board.gov/sec508/508standards.htm
Trace Research and Development Center http://www.trace.wisc.edu/
WAVE (Web Accessibility Versatile Evaluator) http://www.temple.edu/inst-disabilities/piat/wave/
W3C's Web Accessibility Initiative (WAI) http://www.w3.org/WAI/
Oklahoma ABLE Tech based this tutorial on the DO-IT (Disabilities, Opportunities, Internetworking, and Technology) materials on accessible Web design. DO-IT serves to increase the successful participation of individuals with disabilities in challenging academic programs and careers such as those in science, engineering, mathematics, and technology. Primary funding for the DO-IT program is provided by the National Science Foundation, the State of Washington, and the U.S. Department of Education. You may visit their website at www.washington.edu/doit/.
Permission is granted to copy these materials for educational, non-commercial purposes provided the source is acknowledged. However, the contents do not necessarily represent the policy of the federal government, and you should not assume their endorsement. 4/02