Please, keep checking the browser's layout engine against HTML5 support: http://en.wikipedia.org/wiki/Comparison_of_layout_engines_%28HTML5%29
From the table shown in the above article you will see that the Trident engine (http://en.wikipedia.org/wiki/Trident_%28layout_engine%29
]) used in IE still sucks :-).
There is one work-around: you can change the default Web browser used by Visual Studio.
You can find out how to do it in many places:
More importantly, do you really need those HTML5 features if IE does not support them? How about your users using IE? Anyway, you decide.