A Web User's Tutorial:

Volume I, Issue 15 — November 11th, 1996

by Geoff Freed,
CPB/WGBH National Center for Accessible Media

he CPB/WGBH National Center for Accessible Media (NCAM) develops strategies and technologies to make media accessible to millions of Americans, including people with disabilities, minority language users, and those with low literacy skills. The Web Access Project, announced by NCAM in February 1996, was initiated to research, develop and test methods of integrating access technologies (such as captioning and video description) and new Web tools into a World Wide Website, making it fully accessible to blind or deaf computer users. The Web Access Project is made possible by the support of the Telecommunications Funding Partnership for People with Disabilities, and The Boston Foundation.

One of the early goals of the Web Access Project was to develop and distribute a generic, public-domain symbol to indicate that a Website was designed with accessibility features. The symbol, designed by Stormship Studios of Boston, Massachusetts — shown at left — is available free of charge from NCAM's Website, or via anonymous FTP. Website designers can use the symbol to indicate that efforts have been made to accommodate the needs of deaf, hard-of-hearing, blind and/or visually impaired users. Extensive guidelines for designing accessible Webpages may be found at the Trace Research and Development Center.

Movie clips are becoming more and more popular on the Web, yet they present accessibility problems for deaf, hard-of-hearing, blind and visually impaired users. Without much extra effort, these movies may be made more accessible.

Many movie clips found on the Web are based on Apple's QuickTime software standard. These clips are composed of separate video and audio tracks. A separate text track may also be added to a clip, effectively serving as a caption track, making it easier for deaf and hard-of-hearing users (or hearing users lacking sound capability on their computers) to fully understand with is happening in the movie. To see examples of captioned movie clips, playable on both PC and Macintosh computers, click here or on the frame from a captioned movie shown at left. Depending on the software used to play back the movie, the user can actually turn the text track on and off. If the player is not capable of turning the tracks on and off, the text track simply becomes open captions.

In order for a blind Web surfer to fully comprehend a movie clip, key visual elements must be described. In a QuickTime movie, this narration (describing elements such as settings, actions and body language) is recorded onto an extra soundtrack which plays along with the regular program audio. The descriptions are timed not to interfere with dialogue. As with captions, the description soundtrack may be turned on and off depending on the software used to play back the movie. Visit NCAM to see examples of movie clips with descriptions.

For additional information on captioning and description, visit The Caption Center and Descriptive Video Service.

In order to use a computer, a blind person uses a software device known as a screen reader, which reads the text shown on the screen out loud. Unfortunately, screen readers cannot interpret the graphic elements of a Webpage. However, it is a simple matter for a Webmaster to accommodate blind users by accompanying graphics or images with alt-text tags, which identify the images with just a few words. In order for the screen reader to read the alt-text tags, the user must first disable the Web browser's image-loading feature so the alt- text tag appears on the screen in place of the image.

Pictures, graphics or logos should also be accompanied by image descriptions, one or two sentences which provide more detail than alt-text tags. Descriptions can be displayed next to or below an image, similar to a photo caption, or they can be linked to another page. The link itself is usually the word "description" or the letter "D", and is placed next to the graphic. See NCAM for samples of both alt-text tags and image descriptions.

For more information, contact:

Geoff Freed (geoff_freed@wgbh.org)
CPB/WGBH National Center for Accessible Media
WGBH Educational Foundation,
125 Western Avenue,
Boston, MA 02134

(617) 492-9258 (voice/TTY)
(617) 782-2155 (fax)