I have 5 button mouse with 2 scroll wheels (a4tech opto325). I had configured it like this
Section "InputDevice"
        Identifier  "PS/2 Mouse"
        Driver      "mouse"
        Option      "Protocol" "ExplorerPS/2"
        Option      "ZAxisMapping"          "4 5 6 7"
        Option      "Device" "/dev/psaux"
        Option      "SendCoreEvents"  "true"
        Option      "Buttons" "9"
With this config the second scroll wheel works as back/forward in opera and firefox, and scrolls vertically in xpdf and konqueror, both side buttons doesn't work.
When I replace the protocol with IMPS/2 the those buttons are working, but as mmb (left) and rmb (right). This is a little bit annoying i would like to have vertical scrolling on the second wheel (first wheel is working fine).
It would be cool if someone help me to do the side buttons working as back/forward in opera/ff/sth else