This error seems to be a known bug in VS 2012 when you try to set runat = "server", which contains the a element.
Well, I actually use VS 2010 (although it installed 2012 last night, and rumors keep that this will cause it in 2010 as well), and there are no thead or tbody elements in the table elements that supposedly cause this error. But they have an attribute runat = "server" and colgroup.
So is this related to installing VS 2012? And if so, is there a fix for this?
UPDATE: Removing colgroup elements seems to resolve this. However, this is rather annoying.
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