You can look here if you want to change the password or delete the account *https://accounts.firefox.com/settings You can disconnect from Sync by clicking the e-mail address in the "3-bar" Firefox menu button drop-down list or go to "Options/Preferences > Sync". In case of issues with Sync you can try this: Delete the signedInUser.json file in the Firefox profile folder and delete the Weave folder (Sync was formerly named Weave). If that isn't enough then delete the prefs.js files to reset all prefs and maybe also delete the compatibility.ini file to reinitialize the profile. You can use this button to go to the current Firefox profile folder: *Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder) *http://kb.mozillazine.org/Profile_folder_-_Firefox