You don't have to clean up. If they are no longer being obeyed they will just be ignored. You would only remove them if you are redesigning, in which case you r

You don't have to clean up. If they are no longer being obeyed they will just be ignored. You would only remove them if you are redesigning, in which case you remove them as you go. Just make sure if you are currently adding in vendor prefix stuff you add a general case for everyone else now. Future and backwards compatible.