@vesuvius: to monetize a web language have hooks to azure and bing.

Dart, as I understand it, compiles to .js which then runs in the browser. Would C# be able to do the same?

I see Dart is not statically typed ( guessing ) . Is that a requirement of a DOM language? Maybe have it statically typed where all the HTML5 attributes are pre defined. And if you introduce new attributes to the HTML tags you have to declare them somehow to the classes the language uses to represent the DOM objects?