Google encourages you to use XHTML, rather than HTML, for your Maps-utilizing web app. But they didn't seem to think that decision through very well—if your "XHTML" page is sent as a "text/html" document, all is well. But then your browser reads this jibberish in as tag-soup HTML. XHTML should be served as "application/xhtml+xml".
Google Maps uses legacy techniques, like
So, what was the point of encouraging XHTML again?