See https://support.mozilla.com/en-US/questions/840927

thank you for your immediate response. i followed the link you gave me which took me to another answer for another user with a similiar question. in the answer to that question it said to uninstall firefox 5 first then download firefox 4. Well I unfortunately am very computer illiterate & I guess my common sence wasnt working for i uninstalled firefox 5 as it said & now I do not have an internet browser at all. I cannot get my internet explorer to work. I tried to do a system restore back 2 days & its saying there were no changes. Please can you tell me how do I get internet back on my computer when I dont have internet to download from. thanks for any help.

Hey I had the same problem as you & it was 100% completely FIXED after I installed this version of Fast Dial. Do the following:

1)  go to this link ---->   
https://addons.mozilla.org/en-US/firefox/addon/fast-dial-5721/versions/

2) install version "3.5b1"

THAT'S IT!!

btw I did this using firefox 5. If you're still trying to figure out how to install an internet browser back on your computer since you deleted Firefox 5. Then you need to go to a computer with internet connection ---> then go to www.getfirefox.com ----> then click the down load button but SAVE IT to the computer instead of OPEN it. Then move that file onto a disc ----> take the disk onto your personal computer and open the Firefox file from there.

simple

I completely agree with you, having tried very hard not to upgrade to Firefox five I somehow did it by mistake and now all I get is "well, this is embarrassing". It's typical, isn't it? Every time someone tries to improve something they inevitably make it worse or I would say attempts to make satisfactory better generally make satisfactory far worse than it was I wish to God I could get back to Firefox 4.

I completely agree with you, having tried very hard not to upgrade to Firefox five I somehow did it by mistake and now all I get is "well, this is embarrassing". It's typical, isn't it? Every time someone tries to improve something they inevitably make it worse or I would say attempts to make satisfactory better generally make satisfactory far worse than it was I wish to God I could get back to Firefox 4.

It may not be supported but its still hosted.

Firefox 4.0.1

Just change the update options on your first load to not automatically update.

Or even better...Use chrome :)