What price well-formed HTML?!

Thought I'd check whether the HTML in this blog was properly formed ('cos I care about things like that). And I find that the ad banner inserted at the top of the page is full of bad markup (see for yourself). Which means that all the 'free' blogs hosted at Blogger are badly formed - thanks to a small error by (presumably?) one HTML programmer at Google/Blogger. Who says one person can't make a difference...?