The Web Content Accessibility Guidelines (WCAG) 2.0 is based around four fundamental design principles that state that, in order for a website to be accessible, it must have content that is:
- Perceivable. Information and user interface components must be presentable to users in ways they can perceive. This means that users must be able to perceive the information being presented (it cannot be invisible to all of their senses).
- Operable. User interface components and navigation must be operable.
- Understandable. Information and the operation of user interface must be understandable.
- Robust. Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.
Each of the four principles have a number of guidelines that are associated with each principle.
- Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.
- Provide alternatives for time-based media.
- Create content that can be presented in different ways (for example simpler layout) without losing information or structure.
- Make it easier for users to see and hear content including separating foreground from background.
- Make all functionality available from a keyboard.
- Provide users enough time to read and use content.
- Do not design content in a way that is known to cause seizures.
- Provide ways to help users navigate, find content, and determine where they are.
- Make text content readable and understandable.
- Make Web pages appear and operate in predictable ways.
- Help users avoid and correct mistakes.
- Maximise compatibility with current and future user agents, including assistive technologies.
(Source: WCAG 2.0 at a glance)
Top of page