Hmm, i'm not sure if there is an official list or not, i can work on something for that though.
It doesn't assume there is pushState, backbone does browser detection and will try to default to using pushState and fallback to using URL fragments if it doesn't have any. You can also set that as an option in the router, for more info on that checkout
http://backbonejs.org/#RouterI'm pretty sure that it can be supported on most browsers as a majority of the code is dependent on what you want it to do, mostly the Rendr framework focuses on rendering templates to html strings and returning them on the server.