Includes many elderly users.
 

1. Problems with color perception
  Use color redundantly
       Color-code larger areas only
       Colors should differ in at least two primary colors
       For elderly people, allow for more brightness after extended computer work

2. Problems perceiving small objects
  Allow for screen magnification

3. Blindness
  Special I/O devices (Braille , speech output, physical models)
       Special software (e.g, "screen readers", "web-to-speech translators")
       Special accessibility guidelines (e.g., W3C WAI Guidelines )
       Accessibility analyzers: plugins and stand-alone software