We all know Google team is working on its new OS "Google Chrome OS" which will be open source and targeted at Netbooks. It would be available in second half of 2010.
Now it seems Microsoft is coming with a similar thing which is called "Gazelle" currently. "Janie Chang" at Microsoft Research website posted detailed information about Gazelle web browser:
Helen J. Wang, senior researcher in the Systems and Networking group at Microsoft Research Redmond, is working on ways to evolve the browser into an operating system that supports an increasingly sophisticated Web environment.
The Multi-Principal OS Construction of the Gazelle Web Browser describes the design and construction of a browser that is actually a multi-principal operating system.
In the Gazelle model, the browser-based OS, typically called the browser kernel, protects principals from one another and from the host machine by exclusively managing access to computer resources, enforcing policies, handling interprincipal communications, and providing consistent, systematic access to computing devices.
Gazelle essentially leverages the existing mechanisms of operating systems and tailors them to the needs of Web applications. In Gazelle's architecture, the browser kernel is a layer that sits between the underlying operating system and the principals, exclusively responsible for managing principals and system resources.
Gazelle represents the first time that a browser has been implemented as a multi-principal operating system.