What browser should you use?
Over the years we have tried to create websites that are displayed correctly on every browser, and sometimes we did manage to get it correct. But it isn’t that easy to get your application configured and coded so that all browsers react in the same way. Basically it comes down to one thing: Create an application for IE and Firefox and then you’ll probably cover 90% of all users.
Off course all Mac users will feel left out, but, in my opinion, those are the 2 major browsers, and if they work correctly it will probably work in Opera and Safari to. Maybe you need to do some minor adjustments, but you will be finished quite fast. My point is to start off with IE and Firefox because the other way around will give you huge headaches.
I saw a good slide show on this topic by John Resig and it is displayed below. You might want to take a look at it, it’s really interesting.