Web accessibility means that people with disabilities can use the web.
Disabilities that affect access to the Web include visual, auditory, physical, speech, cognitive and neurological disabilities.

Web accessibility also benefits people without disabilities. For example, a key principle of accessibility is designing Web sites and software that are flexible enough to meet different user needs, preferences, and situations.

This flexibility thus benefits other users, such as people using a slow Internet connection, people using new technologies such as iPhones, people with temporary disabilities such as a broken arm and people with changing abilities due to aging.

The W3C Web Accessibility Initiative (WAI) has developed guidelines that are considered the international standard for Web accessibility. Their Web Content Accessibility Guidelines (WCAG) -- now in version 2.0 -- defines how to make Web content more accessible to people with disabilities.

They are designed to apply broadly to different Web technologies now and in the future, and to be testable with a combination of automated testing and human evaluation.

WCAG 2.0 has 12 guidelines that are organized under 4 principles: perceivable, operable, understandable, and robust.
For each guideline, there are testable success criteria, which are at three levels: A, AA, and AAA.

The FAO Web Content Accessibility Guidelines have been derived from WCAG 2.0 because they have been established as a stable, referenceable technical standard.

Web accessibility at a glance

Perceivable

• Provide text alternatives for non-text content.
• Provide captions and alternatives for audio and video content.
• Make content adaptable and make it available to assistive technologies.
• Use sufficient contrast to make things easy to see and hear.

Operable

• Make all functionality keyboard accessible.
• Give users enough time to read and use content.
• Do not use content that causes seizures.
• Help users navigate and find content.

Understandable

• Make text readable and understandable.
• Make content appear and operate in predictable ways.
• Help users avoid and correct mistakes.

Robust

• Maximize compatibility with current and future technologies.