Because IE is slow, has too many popups, and makes an annoying clicking sound every time you load a webpage.
I don't use FF apart from to check sites i've made, same with IE. I use Opera. Might switch when FF3 comes out properly though.
Why you ask? Firefox is faster, more secure, has tabs, easily get addons that you want, no annoying things to slow down like IE has.
Ok, Well I wouldn't know because I don't use the latest IE, I know in past firefox had tabs first. Since that isn't case, then every other thing I mentioned is good enough I suppose
I change to firefox from IE because of the tab and also hundred of plugins to use give the extra credit to firefox.
I recently changed back to IE because I was having problems accessing DP with Firefox. I mostly used Firefox for the added tools but now IE offers most of the same tools so I am happy using IE again.
Out of curiosity I've tried FireFox v1.* long time ago, and since I just couldn't use IE anymore. I'm not sure I can give an explanation but that's just what happened.
Mate, Go to Control panel -> Sounds and Audio Devices. Click the Sounds tab and configure whatever sounnd you want or do not want to hear when you click a link for eg. The Start Navigation one I believe is for when you click a link, not sure about loading a webpage though.