To claim Single A conformance, all of your pages and documents must meet all Single A requirements
To claim Double A, all of your pages and documents must meet all Single A and all Double A requirements
To claim Triple A, all of your pages and documents must meet all Single A, Double A and Triple A requirements
Using images as links is perfectly acceptible, but they do need some special attention. A screen reader can identify images used as links, so they should be placed in the page in a way that this technology can access. This means they must have alt text and it must be relevant.
See also the guidelines for
Images are made into links by wrapping an a tag around the img tag. Luckily this is done automatically by most webpage editing software, but still needs some attention to getting it right.
The image code may have been:
<img src="icon.gif" alt="icon" />
When made into a link, the alt text needs to say where the link is going to take the user. A screen reader will read this out as a link, and use the alt text as the link text. Therefore, it is important that the alt text describes the link purpose, not the image appearance:
<a href="products.html"><img src="icon.gif" alt="Our Products" /></a>
In this example, keeping the alt text as icon' would not be informative.
See also
No specific requirements for making images into links.
No specific requirements for making images into links.