Not sure if this is the place to post this but when you put google into the W3C Validation checker, it get's lots of errors :S http://validator.w3.org/ Fire google into that badboy ^ and see what i mean :
They are obsolete nowadays, but do help somtimes with secondary SE. Anyway it is clear that google can f... about - #1 guarenteed if you search for "google"
Its true that google has alot of validation errors. But if you have a validated site, it always helps...
To be honest, I never care for validations. All we do ASP or ASP.net pages with lot of dynamic functionalities which some times fails. Even Microsoft's site didn't pass the validations. However when we design static pages, we keep validations in mind and try to provide 100% validated site. Still no one on earth is perfect and one should leave scope for human errors.