While it's old - pre html5 this reference has something to say - esp read till the bottom where he points out problems with MSIE (of course "that" browser has to mess things up again).
Why can't Google engineers just learn to program without document.write() ... innerHTML guys ... And why can't adsense support work like they should ... actually answer things and be knowledgeable about their own crap.
in the end it seems like it's not going to happen. I'll probably end up serving the content as html ... which is against the standards ... thanks Google , thanks Microsoft ... I will remember.
Or maybe use the included object if the browser understands xml and use the normal code if the browser only supports html and no xml -IE does that-. But it means all pages have to be server side scripted ... which they have no need to be for any other reason in most cases.