Whenever feasible, try to design a website to be usable by as many people as possible. This can include people who cannot see, or hear, or move their mouse well, or even at all. Here are some hints and tips for accessibility-aware web design.
Step 1: Part I: Visually Impaired Folks
This section is larger than the other two, because web pages are primarily a visual medium.
1. Does your web site make assumptions about how people are going to be looking at your site? Try looking at your web site with large fonts set in your browser. Make sure any non-text visual elements (buttons, images, etc) also scale. Try setting a high contrast color scheme. Still usable?
Did you specify a specific font size, rather than relative size?
Use a percentage of the default font size in your "font-size" style sheet stylings.
Step 2: Visually Impaired Accessibilty Guidelines (cont)
looks for the color blind. And check We are Colorblind for more
The image in the previous step is a full-color version of a common color-blindness test image. The image in this step is a simulated version of the same image as a red/green colorblind person might see it.
3. How does your website look in Lynx?
Lynx is a text-only web browser that is available for a variety of platforms including Microsoft Windows and various flavors of Unix and Unix-like operating systems (including Mac OS X).
Since it's just plain text, Lynx makes it even easy for a user to make a font larger, or to make other adjustments to make the text more readable. Plus, Lynx is great for using text-to-speech processing if a user cannot use the video display at all.
Step 3: Page Navigation for the Visually Impaired
Try to make your page usable -- some sites with flash-based navigation and media-heavy content will also have a static HTML version of the core information available for users.
6. Do you use good ALT tags? Make sure your ALT tags give useful information to the user. "Image of the company mascot - select to proceed to the next page" is a more useful description than "Awesome pic of a happy cartoon dog pointing it's paw to the right." Do you use imagemaps? If so, make sure they're client-side and use ALT tags, so that people can use the imagemap without seeing the image.
Step 4: Part II: Mobility Impaired Folks
2. How about for folks who have trouble with accurate mouse control? Does your website require fine motor control for navigation? This can make it hard for some people to use. If your web page generates pop-up windows or autoscrolls, this can make it harder for these folks to control the display. Make sure someone with, e.g, hand tremors can still navigate your web site.
Step 5: Part III: Hearing Impaired and Deaf Folks
Step 6: Conclusion
Accessible design is good design!
Check out Usability.gov for a general overview of usability and user-focused design from the US government, or the W3C's Web Accessibility group's web page for more ideas.