I support an application that runs in Firefox under Ubuntu Linux 12.04. The computers used for this application are dedicated, not used for anything else. If users open another Firefox window, either via the desktop icon or ^N Ctrl-N or File > New Window and run another instance of the application it makes a mess. So I want to prevent new windows being opened. Also prevent opening new tabs, although the users are less likely to open another instance of the app in a tab. They are doing this (opening multiple instances) by mistake, not maliciously. Removing File > New Window and disabling ^N would help. But preventing 2nd+ launch by icon click is also necessary. It would be nice if an administrator could undo it, even from the Linux command line or by editing a config file. Thank you.