Joel Spolsky writes in Strategy Letter VI

The winners are going to do what worked at Bell Labs in 1978: build a programming language, like C, that’s portable and efficient. It should compile down to “native” code (native code being JavaScript and DOMs) with different backends for different target platforms, where the compiler writers obsess about performance so you don’t have to. It’ll have all the same performance as native JavaScript with full access to the DOM in a consistent fashion, and it’ll compile down to IE native and Firefox native portably and automatically. And, yes, it’ll go into your CSS and muck around with it in some frightening but provably-correct way so you never have to think about CSS incompatibilities ever again. Ever.

To that, Didier Girard replies : what about GWT?

But the answer was right there: it’ll go into your CSS and muck around with it in some frightening but provably-correct way. Compiling Java syntax to Javascript, taking care of the subtle differences between the browsers in the DOM or event handling is relatively easy compared to providing a high-level developper interface for styling while keeping the full power of CSS. And the full power means cascading, and cascading means knowledge of the DOM structure. That, is a hard problem to solve, and there is still nothing promising above the horizon for that problem.