If I fill in a form and then submit it and then return to that form page via a hyperlink or back button, the input fields are now populated with what I put in there in the first place.

How do I prevent this?
What happens is that somebody clicks "logout" on my page and the session is destroyed.
Then if they click "Login Again!" the username and password is remembered by the form.

There's got to be some WML attribute to the input field that I've missed.