If you're going to change a client's index page to a "this person does not pay" thing or whatever, make sure you have made sufficient efforts to contact the client first. If by e-mail, don't delete the sent messages because they may be helpful should you need a lawyer. Then, if they get a lawyer to send you a letter to remove the "nasty" page, you have your butt covered (provided you have a signed contract).

Stand your ground but always be professional about it.