Read here for analytical information:

https://support.mozilla.com/en-US/kb/Installing%20Firefox%20on%20Linux

thank you

Please mark "Solved" the answer that really solve the problem, to help others with a similar problem.

Ok so as I see you're running Linux Mint 10. If you downloaded Firefox from it's official site that's not the best way to do it. Linux distridutions (like yours) have they own softwate collection that you can download from a repository.

So try now to go to an app called "Software Manager" from your system menu. When it opens, there should be a search box, type in "Firefox". When it finds it, just hit the button "install", wait a few moments and there you go. That way you should install all programs on Linux Mint :)