While the world is talking about Google's upcoming Chrome OS set to hit in the second half of 2010, Microsoft's also been working on a secret browser/OS project.
Microsoft's project right now is codenamed Gazelle, and like how Chrome isolates various elements inside their own sandbox, it too will utilize similar security features.
Multiprocess browsing, used by Chrome and even the latest version of Internet Explorer, separates each webpage/tab as its own process. That means that if one page or tab crashes, the other pages opened are more likely to survive, requiring only the offending tab to be closed. This approach is undeniably safer, but also more demanding on system resources.
Gazelle takes it a step further than current browsers by more finely isolating elements of a page according to domain. It's just another step in making everything more secure, which is always a smart decision when it comes to serious business like the internet.