Noone can say that IE doesn't work with HTML5 and noone can say that IE works with HTML5. HTML5 it's not a one big tool, it's a toolset of different objects and properties that provide new/awesome functionality to our browsers. IE9-IE10 supports a lot of those new HTML5 features. To found out if your browser supports one of HTML5 features you can make manual
test or use special lib for example as Modernizr for tests. Also there are special libs to make your old browser (I think even ie6) a better one, so it will understand new html5 tags and even some js functionality.