Is W3C accessibility important for SEO? I’d say yes.
First of all a compliant code is a correct code. This means that the engine bots will be able to scan it properly and index your site accurately.
Secondly, it provides a solid base for creating a DDA compliant site, thus enhancing user experience for all the Web surfers.
Then, if we speak about XHTML the importance of a valid code is even greater, especially when your run a business site that could be accessed via PDA or mobile phone by the always busy businessmen and women of the modern corporations.
W3C compliant code makes SEO a piece of cake. If you have a valid site the chances for higher rankings in the SERPs increase too.
Make an experiment: record your current rankings, then validate your HTML and optimise your page titles and meta descriptions. Go back on the search engines in two-three weeks. Do nothing else in this time: no linking campaigns, no directory submissions. After this relatively short waiting time, check your rankings again. Do you see any improvements? I bet you will.
Certainly, correcting a HTML code is not so easy as it sounds. If you use an automatic correcting tool like HTML Tidy, chances are that the software will ruin your design. I recommend that you correct each page manually. It takes longer, but while you are at it you have the chance to optimise the alt tags and other onsite SEO elements too.
If you need help with this project, don’t hesitate to contact us.