First time: teach them the right way to do that

Second time: you did it again, did you forget the right way?

Third time: we've talked about this before, what's the deal? If this keeps happening, we're going to have to reconsider your employment here as a web developer

Fourth time: last warning

Fifth time: bye

Good people don't do this sort of thing repeatedly. If your organization refuses to get rid of people like that, you shouldn't stay at that place either.