[tadfisher]

Nah, they just plug in the old Trident renderers. "Browser mode" changes the user agent, and "Document mode" changes the renderer. The JS engine remains the same, which is why you always need to test in the real deal.

[esrauch]

Document mode changes JS compatibility, at least in IE9. I doubt they dropped that in IE10.

http://blogs.msdn.com/b/ie/archive/2011/03/24/ie9-s-document...