Ask HN: How do you communicate what your browser compatibility policy is?

Alright HN, maybe you can help me with this:

I am working on putting together a Browser Compatibility/Support document for our company and was wondering if anyone here has a template/example that they used to create their browser support statement?

I found a couple good ones I like:

http://www.bbc.co.uk/guidelines/futuremedia/technical/browser_support.shtml

http://developer.yahoo.com/yui/articles/gbs/

but they don't have any reasoning behind why selected those specific browsers. I am hoping for something that has a bit more information on not just the what but the why behind those selections. And something that communicates that in a nice and convincing fashion to the clients. :)