W3C Validation does not boost SEO
Some people say that webpages that passes W3C validation helps with SEO. Others say that it does not.
Matt Cutts, software engineer at Google on SEO says that W3C validation does give any extra boost in Google search ranking. Watch this video …
This is because the majority of the webpages on the web does not pass W3C validation. Even Google.com does not pass. A webpage can render and be perfectly fine in all the modern browsers and still not pass W3C validation. This is because W3C validation can be a little too strict and too much of a stickler on certain arcane rules that sometimes is just purely academic.
It take time to tweak code to pass W3C validation — time that might be better spent performing other optimizations.
Here is what SearchEngineJournal.com have to say about W3C validation.
Although it is a good idea to strive for W3C validation if there is time; however, it may not give a major boost in search engine ranking. Unless of course the code is really bad where search engines can not decipher it. Then that is a different story where cleaning up the code can help with search engine results.