The Visually Impaired Web User's Technology
Web developers tend to design for their own equipment. Using a fast computer and a state-of-the-art browser, they turn their web site into a fabulous work of art. But viewing it with last year's browser the thing looks . . . pitiful.
What are most users coming to the site with? Last year's browser. If you are sufficiently arrogant, you might stick a "Best viewed with" message on your front page and just say it's the user's technical backwardness that's at fault. But if you want "most visitors" to come to your site, and you want blind users, you need to consider the diversity of technology that makes up the Internet community.
While reading guidelines and creating a web page, the process of making your page accessible will be more comprehensible if you understand how people with visual impairments are likely to visit your site. What technology is in use and how it works has been a significant part of making guidelines that meet the needs of both web page developers and web page users.
Computer users who are blind usually use a screen reader for most computing activities. This, in simple terms, is a piece of software that "figures out" what is on the screen and sends information to a speech synthesizer to be spoken or to a Braille display. The screen reader provides not only output but to some extent an improved (from the blind user's point of view) interface. The screen reader is the brains of any talking computer. For a more detailed explanation, see the article on Synthetic Speech Systems.
If the user is indeed using a screen reader, then he or she is also probably using a mainstream browser. Common choices among screen reader users are Internet Explorer, Netscape, and Lynx. You'll probably recognize these as among the most commonly used browsers you find visiting your site in general, and blind users will benefit from conscientious support of these browsers as much as will other users.
When a screen reader reads a web page, what is it reading? There are a couple of scenarios. One is the sophisticated use of a special collaboration between Microsoft Internet Explorer (IE) and some screen readers. IE is able to pass along structure and other information to the screen reader, so some of them can read the web page "intelligently." For example, if you use frames on your web page (strongly discouraged, by the way), JAWS for Windows or Window-Eyes (two popular Windows-based screen readers) will read each frame in turn, including the title of the frame, if you remembered to give each a title.
Some other screen readers, or any screen reader used with a browser other than Internet Explorer, will be unable to get structural information about the web page. So, a navigation frame down the left side of your page will not be distinguished from the article in the main frame. A screen reader used with Netscape, for example, will read the page left to right, top to bottom, the way it reads e-mail or word-processed documents. So, the navigation links are mixed together with the text of the article.
Another group of users might not be using a screen reader at all to access your web page. Instead, they might visit your site with a browser designed specifically for blind users. In this case, the browser should be able to discriminate the structure of your page, to the extent that the page has a structure, and pass the information on to the user in a meaningful way. The down side to special browsers is that their development typically lags the development of the more popular browsers. So, they may not support the hottest new animations, security, or other innovations you want to use on your site.
Screen Magnification and Other Techniques
Not all users with visual impairments use speech to access your web site. The majority of users will have some sight and will either use a screen magnification program or rely on features built into the operating system or the browser to enhance the visibility of your web site. For these users, your choice of color and layout can make an enormous difference in their experience of your page.
A screen magnification program makes text and graphics on your web page bigger. Unfortunately, this usually means that the user sees only part of the screen at a time, so must move the viewing area around in order to see everything. This sometimes means that the relationships between items on the screen get lost.
You may have a heading or label on the left and then text or graphics to the right of it. The user, seeing only the left, then only the right, may easily fail to understand that these two are related. For more information about screen magnification, please see the article on Magnification Programs for the Computer Screen.
Users with enough sight to read much of the text on the screen without using additional equipment or software often adjust the colors and sizes of text and icons in order to make them more visible. For these users, one of the several high-contrast color schemes in Windows may be enough to enable them to do word processing and other computing tasks. On web pages, however, page authors often use low-contrast color schemes and other visual characteristics unfriendly to visitors with low vision.