Website which labeled passed a W3C conformance level, might be inaccessible.
Fo example, WCAG2 Level AA Conformance:
Pages bearing this logo indicate a claim of conformance by the page author or content provider to conformance Level AA of the W3C Web Content Accessibility Guidelines 2.0, including all Level A and AA success criteria defined in the Guidelines. The Web Content Accessibility Guidelines 2.0 explain how to make Web content accessible to people with disabilities. Conformance to these guidelines will help make the Web more accessible to users with disabilities and will benefit all users.
Claims are not verified by W3C. Content providers are solely responsible for the use of these logos.
Online accessibility checkers are not enough. Accessibility evaluation still needs human or targeted–users testing. What might have been the problem? Is it easy to use and understand?
Check it the full list on Understanding Readability based on WCAG 2.0 (Dani Iswara .com). In my opinion, these list is barrier for human access:
- Not using the clearest and simplest language appropriate for the content.
- Centrally aligned text.
- Text that is fully justified (to both left and right margins).
- No limiting text column width.
- Chunks of italic text.
- Overuse of different styles on individual pages and in sites.
- Links aren’t visually distinct.
- Not using images, illustrations, video, audio, or symbols to clarify meaning.
- Not providing practical examples to clarify content.
- Using a white background behind black text.
- Not using upper and lower case according to the spelling rules of the text language.
- Overuse of unusual foreign words.
- Not using valid clickable links.
- No information about how to contact the Webmaster.