Seeing as people use it to send credit card infomation, you'd need be real uptight about security, and also get a https certificate :S you could make a private message system though.
I'd encrypt the message and store it with a key for decrypting, then save a password the user chooses too, then if password matches, decrypt message, otherwise return blank.
Also, nobody will give you source code, you have to learn to do something, you dont have people helping you walk, do you?
1) Lose the flash banner. Musical websites are the first sign of an amateur and do nothing but annoy people. Replace it with a static image or something.
2) Get someone to proof read it. There are several grammatical mistakes.
3) Test the website on multiple browsers. There are a few graphical problems with certain browsers.
5) Get someone to check your code to ensure that it really does work.
Just some tips.