Start the program
xev in a terminal. Move the mouse inside the
xev window; you’ll see a lot of stuff scroll by. Press each button in turn. Then switch back to the terminal window and press Ctrl+C.
xev shows a description of each input event, in particular
ButtonReleasefor mouse clicks (you’ll also see a number of
MotionNotify for mouse movements and other events).
It’s likely that your forward and back buttons are mapped to mouse buttons, maybe buttons 8 and 9:
ButtonPress event, serial 29, synthetic NO, window 0x2e00001, root 0x105, subw 0x0, time 2889100159, (166,67), root:(1769,98), state 0x0, button 8, same_screen YES
If that’s the case, remap these buttons to a different action in your browser; or to disable the buttons altogether, put these lines in a file called
! Disable buttons 8 and 9 pointer = 1 2 3 4 5 6 7 0 0
Test it with the command
xmodmap ~/.Xmodmap. Most desktop environments and window managers run this command automatically when you log in; if yours doesn’t, arrange for it to run when X starts.
It’s also possible that your mouse sends a keyboard event when you press these buttons:
KeyPress event, serial 32, synthetic NO, window 0x2e00001, root 0x105, subw 0x0, time 2889100963, (957,357), root:(2560,388), state 0x0, keycode 166 (keysym 0x1008ff26, XF86Back), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: False
In that case, put lines like these in
keycode 166 = NoSymbol keycode 167 = NoSymbol
Helpful link: Reprogram mouse buttons