Hi bollamvenu Any particular reason or example ? This is probably not really a Firefpx question because you probably also need to stop a user using another Firefox profile, or installing another copy of Firefox or some other browser. What about running Firefox portable from a memory stick, or for that matter booting a whole new OS from an external device. If for instance you are trying to limit schoolkids activity you need to be aware they may well understand a lot more about computers than you or I do. If you suceeed then what do you do to prevent access from an internet cafe or a friends device, or the now ubiquitous smartphone. Now I may be way off the mark with this reply but that is why I was wondering what the problem is that this may solve ?