First, read this: https://launchpad.net/ubuntu/+source/xorg/+bug/52288
Then, read this: http://ubuntuforums.org/showthread.php?t=252467
The second link appears to be a user having the exact same issue as you, with the button doing the wrong action in Firefox.
Below is a chunk fo their xorg.conf for the mouse. It's the same mouse, so evidently it uses the "ExplorerPS/2" protocol. The "Protocol" tells the X server something about what sort of mouse it is, and how to communicate with it. I don't really know the guts of it, but if ExplorerPS/2 works for you, then that's the important part
Notice the button mapping they put there; that is how they fixed the problem you are having; they switched a few buttons around.
Your current xorg.conf has no mouse section, and no keyboard section, which is fine until you need to do something like this
so you will need to add the mouse section as described below:
Identifier "Configured Mouse"
Option "Device" "/dev/input/mice"
Option "Protocol" "ExplorerPS/2"
Option "ZAxisMapping" "4 5"
Option "Emulate3Buttons" "true"
Option "Buttons" "8"
Option "ButtonMapping" "1 2 3 8 6 7"
As far as I recall, /dev/mouse and /dev/psaux both point to the same place. However, these usually are used for PS/2 mouses, not USB mouses; USB mouses commonly (not always) use one of the /dev/input/mice sort of entries. If you only have the single mouse connected, then if it were me, I would try /dev/input/mice first. You could unplug the mouse, and run `udev-monitor
` or `udevadm monitor --kernel
` in a console, and with that running, plug in the mouse and note on the console which USB address the device is being connected to, but this is maybe more than you will need to do. Let's hope it's /dev/input/mice.
before trying ANY of the above, why not try using `xmodmap` as it might end up being much simpler:
EDIT: I made a typo -- the corrected line is like this:
shell# xmodmap -e "pointer = 1 2 3 4 5 8 6 7"
and see if that fixes it right there on the spot.
If it does, you can just add that line to one of your boot scripts. If it works, but makes the buttons wrong in a different way, then again, you'll need to fiddle around with the ordering of the 6,7,8 buttons.
Oh, and BTW - I don't know of any way to make this change directly within Firefox, because Firefox receives its inputs via the X server, so one way or the other, you need to fix it with X, not Firefox.
Best of luck!