No, it's not about Internet Explorer vs Firefox. If you surf the Web on your mobile phone, here's the best mobile Web browser that you can get for free--Opera Mini.
How do you get Opera Mini? Open the Web browser on your phone and enter the URL http://opera.com. Click on "Get Opera Mini" (NOT Opera Mobile) to download the fantastic Web browser.
I use Opera Mini to do regular checks on the five Internet portals that I'm currently operating, and its rendering quality is clearly a lot better than the Web browser that's built into my Nokia N73. Try Opera Mini and your phone's built-in Web browser on one of my portals and you'll see what I mean: http://www.overseassingaporean.sg