Boxes And Arrows : The Design Behind the Design

I’d like to hear if anybody has seen any articles or just simple numbers showing that developing and testing on X number of browsers and platforms seems to take an additional XX% of time in development and testing, etc. I have a client that wants to know how much more effort it will take to develop and test a public-facing product that will need to work on AOL, Netscape, IE, Firefox, Safari, etc.

I know the first question should really be which browsers are above the loose standard 1% mark, but we just need to give them ballpark estimates on what they’re asking for.

This does not include accessibility (508).