An additional benefit of website accessibility is an improved performance in search engines. The more accessible it is to search engines, the more accurately they can predict what the site's about, and the higher your site will appear in the rankings.
Not all of the accessibility guidelines will help with your search engine rankings, but there are certainly numerous areas of overlap:
1. ALT descriptions assigned to images
Screen readers, used by many visually impaired web users to surf the web, can't understand images. As such, to ensure accessibility an alternative description needs to be assigned to every image and the screen reader will read out this alternative, or ALT, description.
Like screen readers, search engines can't understand images either and won't take any meaning from them. Many search engines can now index ALT text though, so by assigning ALT text search engines will be able to understand all your images.
2. Text displayed through HTML, not images
Text embedded in images appears pixelated, blurry and often impossible to read for users utilising screen magnifiers. From an accessibility point of view this should therefore be avoided.
Search engines equally can't read text embedded in images. Well, you can just give the image some ALT text, right? Unfortunately, there's strong evidence to suggest search engines assign less importance to ALT text than they do to regular text. Why? Spammers. So many webmasters have been stuffing their ALT tags full of keywords and not using them to describe the image. Search engines have cottoned on to this form of spamming (as they eventually do every form of spamming) and have taken appropriate action.
3. Descriptive link text
Visually impaired web users can scan web pages by tabbing from link to link and listening to the content of the link text. As such, the link text in an accessible website must always be descriptive of its destination.
Search engines place a lot of importance on link text too. They assume that link text will be descriptive of its destination and as such examine link text for all links pointing to any page. If all the links pointing to a page about widgets say