Some mice may have problems with Firefox because you don't have the latest device drivers, which allows your computer software to interact with your mouse.

Logitech

Some old Logitech™ mouse drivers are known to have problems with Back and Forward buttons not working in Firefox.

1. Select the product type and name at the Logitech™ Support downloads page.
2. Enable the Back and Forward buttons to work in Firefox, by using the instructions in this Logitech™ tutorial.

Based on information from Logitech mouse (mozillaZine KB)

In Firefox 3 on Linux, the mouse button assignments for Back and Forward have changed, to follow X11 customs. Previous versions of Firefox used buttons 6 and 7 for Back and Forward, respectively. Firefox 3 uses buttons 8 and 9. You can configure Firefox to use 6 and 7 by editing some hidden preferences.

1. Type about:config in the address bar and press EnterReturn.
   A warning page may appear. Click Accept the Risk and Continue to go to the about:config page.
2. In the Filter: box, type mousewheel.horizscroll.withnokey.
3. Double-click on mousewheel.horizscroll.withnokey.action, set the value to 2, and click OK.
4. Double-click on mousewheel.horizscroll.withnokey.numlines, set the value to -1, and click OK.
5. Double-click on mousewheel.horizscroll.withnokey.sysnumlines, which should set the value to false.

You can now close the about:config page.