f you have severe difficulties with your vision, then you are probably reading this column at a computer and not from a piece of paper. That's because computers offer more flexibility for people with vision disabilities then printed page ever could.
If you have poor eyesight from old age or an accident, you can correct for it somewhat by telling your computer to display text with a much larger font. Another approach is to tell your computer to use display with high contrast, so that instead of showing windows with colors and subtle shades of gray, everything is displayed in stark white and black. And if you have no eyesight at all, a special program called a screen reader can read to you all of the text on your computer's display.
Consider the case of Paul Parravano, co-director of the Office of Government and Community Relations at the Massachusetts Institute of Technology, who has been blind since birth.
''About two years ago, I called the MBTA,'' recalls Parravano. ''I had just moved, and I wanted to get some bus schedules in accessible form. They said, `Well, we can to get them in Braille.' I said that sounds bulky, but let's try it.''
Although Braille is a wonderful invention for the blind, it's not the best way to carry around a bus schedule. Braille books and printouts are typically much bigger than their printed equivalent, because Braille letters need to be embossed large enough so that they can be felt with a fingertip.
Parravano really wanted the bus schedules in electronic form, so he could load them into his hand-held computer, which has a synthesized voice feature. Once inside the machine's memory, he could instantly search through the bus schedules and listen to them anywhere.
As it turned out, the MBTA didn't have the bus schedules in Braille, so they called the National Braille Press and asked what to do. Parravano learned of the call because sits on the group's board. ''I called the T back and said, why don't you just give me a disk of the schedules?''
After considerable struggle, the MBTA finally got Parravano a computer disk with the information - but it was in a format that his computer couldn't understand. Then, from a different source, he learned that the MBTA had a Web site. ''Sure enough, I punched up the bus number that I wanted and there it was,'' he said. With a few more keystrokes, he downloaded the schedule and many more into his portable computer.
Stories like these are becoming more and more common as businesses, governments, and universities rush to put as much information on line as they possibly can. Few if any of these organizations set out with the express goal of making their information available to the blind. But accessibility has been a happy side effect for the blind.
But the Web is not a panacea. If businesses, governments, and other organizations that publish information on the Web don't pay attention, the Web's promise of equal access for all could be fatally undermined by the rush to make Web sites technologically slick and visually exciting.
The problem is graphics. If you are one of the nation's 450,000 people who are totally blind, the only part of a Web page that your screen reader can say aloud is the text. Unfortunately, many Web sites are fond of taking text and turning it into a stylized little graphical image.
Graphics let the Web site precisely control what's seen on the Web browser's screen, but it makes the information inaccessible for a person without sight.
Text that's turned into graphics is also a problem for the 2 million Americans who have severely impaired vision. Even if you tell your browser to display all text with big 24-point fonts, images stay the same size.
In April, the Web Accessibility Initiative at the World Wide Web Consortium (www.w3.org/WAI) issued a number of guidelines for Web sites designed to make them more accessible for the blind and visually impaired. Many of the guidelines are common sense, such as item 1.5: Avoid Blinking or Scrolling Text.
Web sites that rely on Java or JavaScript to display information should make the same data available in plain text. Not only are Java and JavaScript bad for screen readers, but many people either turn these languages off or else access the Web with browsers that don't support these technologies.
But probably the most important guideline is item 2.1: Provide alternative text for all images and image maps. If a Web site provides alternative text for each image, then people who aren't looking at the image will still be able to figure out what each Web page means. This is important for people who can't see images and for people who turn off images to save on downloading time.
To this end, you can simulate what it's like to be a blind person reading the Web by telling your browser to skip downloading graphics. Under Internet Explorer, select Internet Options from the View menu, click on Advanced, check the box that says Always Expand Text for Images, and uncheck the box that says Show Pictures.
If you use Netscape Navigator, you can accomplish the same ends by clicking Preferences from the Edit menu, clicking on the Advanced category, and then unclicking the box that says Automatically load images.
If you are a Web designer, you might want to leave your browser set up this way for a week or so. You'll quickly gain a new appreciation for which Web sites are doing a good job, and which don't have a clue.
For example, the MBTA (www.mbta.com) has gone out of its way to have a graphics site and a text-only site. That's good. But if you go to the text-only site and click on Subway, the site quickly becomes unusable. That's the result of poor planning.
Technology writer Simson L. Garfinkel can be reached at plugged-in@simson.net.
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