FireFox misinterprets your left/right movements along the bottom of the touch pad as your desire to move forward and back in your page history. This can be VERY annoying. There are 2 solutions to this:
1. add this line to your xorg.conf file in the 'synaptic' device section
Option "HorizScrollDelta" "0"
2. edit FireFox to stop doing this behaviour (this is my recommendation as it is not a system wide change)
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In firefox type in the address about:config. Double-click the line mousewheel.horizscroll.withnokey.action. Set it to 0 (2 is forward and back pages. 1 enables Horizontal scrolling). Set mousewheel.horizscroll.withnokey.sysnumlines to true.
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I found this solution at http://gentoo-wiki.com/HARDWARE_Synaptics_Touchpad
