Does Firefox just not start up now? Or is there something inside Firefox that isn't working for you now? Please read Basic Troubleshooting, and see if that helps you out. If it doesn't let m know what you are trying to do that isn't working.

Hi, thank you for reply. The browser starts with a blank page, but no site can be displayed, i have no search engines and the up menu have some trouble. I have tried to change the network settings from the preference window but the buttons don't work when I click them. I have tried to delete and reinstall it but nothing has change