Open /home/user/.mozilla/microb/prefs.js anyway you prefer personally im using WinSCP. Close ALL browser windows or to be sure "killall browser" in terminal. Now add fallowing lines to the pref file: user_pref("network.protocol-handler.warn-external.sip", false); user_pref("network.protocol-handler.warn-external.tel", false); Now reboot without starting the browser and everything should work just fine.