ok this may sound stupid but bare with me or explain how it can't happen.

ok you have a user, they cruise to some site and look through the shopping cart and find what they want. now they go to sign up and the page the generates the form is for paypal.

what is stopping the user from coping that page and saving it to there hard drive and editing the hidden form elements and adjusting the price, or anything else for that matter, then send it along like nothing happened???

is there a way to hide the forms hidden elements? because some of the hidden elements are needed to complete the process of signing up through paypal.