Firefox

i had the same problem before and eminent problem also on some win7 machines. try to re install your firefox, defrag you disk and do some virus scans..

First do a scan for virus's, trojans and I do this also I also scan for malware, all of those can slow down your browser. Second, clean all cookies and temp files, I have a program I use to do this called Ccleaner, it is free to download and use. Third, it may be the add ons, but check for the updating on these, if you have auto-updating that can slow you way down if you have alot of add-on's, theme, and plugins. Like Adobe if you have any of those with Firefox it can slow you down with just scanning for the updates. Also if you have Yahoo toolbar running it is probably logging into your account as well. I won't add yahoo toolbar, I just don't because it takes alot time to get it running and it slows my over all performance. If nothing else try write down all your add-ons, do with anything you have added. Go to the basic browser and if it is still to slow, it may be your system not the browser that is the problem.

first, check about how many toolbars are installed in your firefox, 2nd is check for how many add ons are installed in your firefox, 3rd, check for viruses in your computer, 4th is check maybe you are running low on disk space. i have this problem too same as you, i solved it by removing some add ons. themes and toolbars on my firefox :D

Sometimes Firefox seems to run slowly for me also. I try to keep deleting my cookies that helps, along with some of the other suggestions that have been made here!

Remove few add on and also delete all the off line contents and cache stored on firefox.