WCAG 2.0 is a set of guidelines created by the W3C-WAI working group. They have created a set of rules to assist web developers, designers, and content authors create accessible websites. The guidelines are grouped into 4 main categories, known as Principles. They are as follows:
- Perceivable
- Operable
- Understandable
- Robust
Principle #1: Perceivable
http://www.w3.org/TR/WCAG20/#perceivable
Principle #2: Operable
http://www.w3.org/TR/WCAG20/#operable
Principle #3: Understandable
http://www.w3.org/TR/WCAG20/#understandable