It refers to the ability to access the Web and its contents by all people regardless of the disability (physical, intellectual or technical) they present or those arising from the context of use (technological or environmental). This quality is closely related to usability.

When websites are designed with accessibility in mind, all users can access content on equal terms. For example, when a site has semantically correct XHTML code, images are provided with equivalent alternative text and links are given meaningful names, allowing blind users to use screen readers or Braille lines to access content. When videos are captioned, hearing-impaired users will be able to fully understand them. If the content is written in simple language and illustrated with diagrams and animations, users with dyslexia or learning disabilities are better able to understand it.

If the text size is large enough, visually impaired users can read it without difficulty. Similarly, the right size of buttons or active areas can make it easier to use for users who cannot control the mouse precisely. Avoiding actions that depend on a particular device (key press, mouse click) will allow the user to choose the device that is most convenient for them.

Limitations

Limitations in the accessibility of Web sites can be:

• Visual: In varying degrees, from low vision to total blindness, plus problems distinguishing colors (Color Blindness).
• Motor: Difficulty or impossibility to use the hands, including tremors, muscular slowness, etc., due to diseases such as Parkinson’s, muscular dystrophy, cerebral palsy, amputations…
• Auditory: Deafness or hearing impairment.
• Cognitive: Learning difficulties (dyslexia, dyscalculia, etc.) or cognitive disabilities affecting memory, attention, logical skills, etc.