I googled this topic and I came across with three different ways to configure browser capabilities: browscap.ini, browserCaps element in web.config and .browser files in App
The best answer is feature detection, not browser detection! This is particularly true in the day where Firefox & Chrome are putting out releases ever few months and mobile browser use is growing. Use Modernizr (http://Modernizr.com) or an equivalent library to detect the features you are interested in.