Do you mean JavaScript or Java? They are two completely different things.

If you are looking for a Javascript one, have a peek here: http://javascript.internet.com/passwords/prompt-in.html.

PLEASE BEAR IN MIND THAT PEOPLE CAN LOOK AT YOUR JAVASCRIPT CODE AND THEY CAN ALSO DISABLE JAVASCRIPT ON THEIR BROWSER! I WOULD SUGGEST THAT YOU LOOK AT JACOB'S VERSION UNLESS YOU ARE ABLE TO USE PHP!!