After a long time in development, WCAG 2.0 is now a W3C Recommendation. A two-sentence summary (from the W3C WAI WCAG Overview) is "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."