Just because something is not *vital* doesn't mean we shouldn't at least try to do it. It's not vital to comment your code when programming but it's a good habit. A page that normally validates makes it a lot easier to spot problems or errors if it suddenly stops being validated. Google has bigger issues than validation, like trying to compress their html files as much as possible (they avoid quotes in attributes for this reason) since every byte cost them thousands. If it wasn't for some of these special needs, I'm sure they'd try to validate their pages too.