of what i know of IE suffers from certain memory leakage issues and that alone makes you write more careful JS code, that is if you are aware of them. So, if you can avoid these and achieve satisfactory functionality between all recent versions of IE (especially when putting these on their limits) , you can later fix your code working for Mozzila. Of course you could do it simultaniously but would it worth to lose even more time in cotrast of going online. (not a .NET. fan)