Styled+ for Firefox 2.0

Safe - only one app to add many Styles and new unique features without touching any of your personal data: history, bookmarks, addons, permissions and settings (your custom 'chrome' folder, if any will be saved in the Backups > 'FirstRun' folder during the setup)
Standalone - all the images and the about 400 .css rules are embedded locally - customize your browsing experience without any waste of internet bandwidth, simply no needs to silently connect to any data hosting or repository and naturally you can work offline keeping your costumizations
the setup is only needed for easy pointing to the profile in use - to clear from the system just delete the 'Styled+ for Firefox' folder in the profile (and the shortcuts in Desktop and SendTo )
Plus - the plus sign in the app name is for 'add': not only Styles but also new features and naturally the sign: ' + ' is also meaning: ' we want more ! '
... and if you are sticking to an old version of Firefox because of the User Interface customization try 'Styled+ for Firefox' then you'll be ready to upgrade to the Firefox Quantum latest version
... revamp the lost & the last special features !