What is WAI, A, AA and AAA ?

There are three levels of accesssibility compliance. They are A (the lowest), AA (the middle) and AAA (the maximum).

Level A - Priority One

A webmaster who wishes to have a WCAG compliant site MUST attain at least level A. This is also known as Priority One. Every Priority One checkpoint MUST be completed in order to claim Level A Compliance status.

Level AA - Priority Two

A webmaster who wishes to have a WCAG compliant site SHOULD satisfy all the Priority Two checkpoints. This will mean that more barriers to accessibility will be removed for users with disabilities. Once a webmaster has satisfied all the Priority One and Priority Two checkpoints then the site can claim to be Level AA Compliant.

Level AAA - Priority Three

A webmaster who wishes to have a WCAG compliant site MAY satisfy all the Priority Three checkpoints. This will mean that more barriers to accessibility will be removed for users with disabilities. Once a webmaster has satisfied all the Priority One, Priority Two and Priority Three checkpoints then the site can claim to be Level AAA Compliant.