Jeremy Keith has smart things to say about browser support.
I’ve been screwed over in the past by saying “we’re going to support IE9, IE10 and all versions of Firefox, Safari and Chrome that people actually use”. I’ve done this based on solid data—basically, going to Google Analytics, dumping the data out and applying the Pareto Principle and a craptastic Python script I have that extracts the information I need out of the morass of Google Analytics mess.
By ‘agile’ in this context, I mean simply that it is built with technologies that make it easy to adapt to change based on feedback from design and front-end developers. Like, say, Django or Rails rather than Spring, and deployed on Heroku (at least during development) rather than some half-baked ops process. ↩