Nielsen Norman GroupEvidence-Based User Experience Research, Training, and Consulting
A strict focus on accessibility as a scorecard item doesn't help users with disabilities. To help these users accomplish critical tasks, you must adopt a usability perspective.
The key difference between user interfaces for sighted users and blind users is not that between graphics and text; it's the difference between 2-D and 1-D. Optimal usability for users with disabilities requires new approaches and new user interfaces.
Flash designs are easier for users with disabilities to use when designers combine visual and textual presentations, minimize incessant movement, decrease spacing between related objects, and simplify features.
Users aged 65 and older were 43% slower at using websites than users aged 21–55. This is an improvement over previous studies, but designs must change to better accommodate aging users.
With current Web design practices, users without disabilities experience three times higher usability than users who are blind or have low vision. Usability guidelines can substantially improve the matter by making websites and intranets support task performance for users with disabilities.