So if it's OK for Google to skip on standards, it's OK for the rest of us too. right?
Whether or not you decide to ignore standards - there may or may not be consequences. And if there are consequences, you still might have perfectly valid reasons for accepting those risks.
For a long time, arguably even till now, Microsoft didn't pay enough attention to web standards. They made a business decision for whatever reasons which is their perogative. One of the consequences is that they've lost a lot of browser market share. Whether that matters to them or not I don't know.
I suspect that Google balanced the benefits and harms of strict adherence to HTML and CSS standards and found that, for that page at least, it would be much worse to be anal about standards and the impact to the user, if they didn't meet the standards, would be pretty much nil.
Makes sense to me.