xmodmap -e "keycode 105 = slash question"

Hello, dear support forum. I'm running Firefox 28.0 on Debian GNU/Linux 7.4 (wheezy), installed on a Lenovo Thinkpad X200 with ABNT2 brazilian portuguese keyboard layout. In this keyboard, the slash/question key corresponds to Keycode 105, which is not standard to ABNT2 keyboard, and so I have to manually map the symbols to the key using xmodmap: xmodmap -e "keycode 105 = slash question" This works perfectly in all graphical programs, with exception of Firefox. In firefox, the effect of pressing that key is the toggling of Add-on bar. The keyboard shortcut for Add-on bar toggling is CTRL+/, but in this case I am not pressing CTRL at all. It seems as if in Firefox that key is always under the effect of CTRL key. Indeed, if I map, for example, the letter "a" to the key code 105, then when I press that key alone on firefox I get the effect of "select all" (CTRL+a). That does not happen in any other browser or graphical program. My workaround has been to use AltGr+q for "/", and AltGr+w for "?". Any ideas? Thanks a lot!