[Freesteyelz]

You don't need a copyright notice anywhere (site or in code) for copyright protection, at least here in the U.S. It's really for public view. Though, having it does make a work, such as a site more professional (perception is key).

As for legal issues, I also recommend contacting a lawyer who specializes in the area to help you set up. It may also be a good idea to do research on Digital Millennium Copyright Act (DMCA). Consider how the sellers'/consumers' sensitive information will be stored. A third-party, secure off-locaton is often standard.