The free report by Nielsen Norman Group (otherwise valued at $124) based purely on empirical evidence from user testing contains:

• Results of usability tests of 19 websites with users with several different types of disabilities who are using a range of assistive technology:
  • blind users using screen readers
  • blind users using Braille readers
  • low-vision users using screen magnifiers
  • motor-impaired users
• Test data collected mainly in the United States, with some additional studies in Japan to ensure the international applicability of the recommendations
  • A total of 104 users participated in the usability studies:
  • 84 users with disabilities
  • 20 non-disabled users who served as a control group
• 75 detailed design guidelines

The report is richly illustrated with 46 screenshots of designs that worked well or that caused difficulties for users with disabilities in the usability tests as well as 23 photos of assistive technology devices. The examples and guidelines are directly based on empirical observation of actual user behavior.

This report addresses the usability of websites and intranets and addresses the second level (good usability after ensuring technical accessibility).

Beyond ALT Text: Making the Web Easy to Use for Users With Disabilities