Web accessibility refers to the practice of making Web pages accessible to people using a wide range of user agent devices, not just standard Web browsers. This is especially important for people with disabilities such as colour blindness; in order to access the Web, such people require special devices in addition to (or instead of) a standard browser.

The disabilities that Web accessibility is intended to deal with are:

• visual impairments including blindness, various common types of poor eyesight, various types of colour blindness;
• motor impairments, e.g. Parkinson's Disease, muscular dystrophy, cerebral palsy, stroke;
• cognitive impairments, e.g. poor short-term memory (as commonly caused by senile dementia), dyslexia;
• deafness or hearing impairments.

In the UK, the Disability Discrimination Act 1995 (DDA) does not refer explicitly to website accessibility, but makes it illegal to discriminate against people with disabilities. The DDA applies to anyone providing a service; public, private and voluntary sectors. The Code of Practice: Rights of Access - Goods, Facilities, Services and Premises document published by the government's Disability Rights Commission to accompany the Act does refer explicitly to websites as one of the "services to the public" which should be considered covered by the Act.