There's lots of talk today about the new proposed X-UA-Compatible header which is being driven by the WaSP-Microsoft Task Force. The goal of the proposed meta tag header is to provide future compatible for IE and other browsers. The idea is you add a tag to your HTML that locks in browsers to that capability mode:
The above tag theoretically would prevent Internet Explorer 9 or Firefox 4 from breaking because of changes to their standards support by making the run just like prior versions.
While the goal is a noble one, I actually see this causing more harm than good. From past experience, something tells me that future products won't get backwards compatibility 100% correct. Since the whole point is to prevent sites from breaking with future releases, what problem have you solved if the browsers going to have bugs rendering in a compatibility mode anyway?
I like the idea that browser vendors (especially Microsoft) are trying to make web development more future proof, but I think there's got to be a better solution.