Ivan Ristic has posted a proposal on his blog called: Secure Browsing Mode [PDF].

In the document Ivan lists some of the possible effects of his proposal:

• Eliminate Cross-Site Request Forgery.
• Eliminate off-domain information leakage.
• Eliminate session-based attacks (session fixation, session hijacking, session token prediction, etc).
• Make phishing more difficult.
• Eliminate web site spoofing (e.g. through DNS attacks).
• Increase security in shared-browser environments.

I think this is a big step in the right direction, however getting giants like Microsoft and Apple to support it would be the biggest hurdle.

Another hurdle to adoption is that it adds work for web developers. They would have to define the security policy for the site, and send some extra headers back. This is a problem because programmers are lazy, and I have also noticed that security is sometimes a tough sell, unless there is big pressure from above developers don't tend to go to great lengths to ensure security.

Anyways I hope Ivan moves forward with his proposal, and starts working on an RFC that specs things in a little more detail.