[marti]

I agree, embedding a browser doesn't seem lightweight at all. What it does give, however, is a common and comprehensive framework for laying out and styling your UI elements. Every web developer can now be a game UI designer.

Some of the benefits I see with HTML+CSS(+JS) based UI:

  * Comprehensive feature set
  * Easy prototyping
  * Easy modding
  * No recompilation required
  * Web full of documentation & examples
  * Common skill for developers/designers

The main disadvantage is probably the performance hit of having a full-blown browser engine in your game, but it seems to work OK for AAA games. I believe Anno 2070 uses Awesomium for some of its content: http://www.posidyn.com/games/anno2070/anno2070-09.jpg