Generally speaking, copyright is a form of ownership that applies to the text, graphics, design, and other content on your Web site. As long as you have an ownership claim on all of the content on your Web site, you also automatically hold a copyright on that content. You don't have to register your copyright with the government to protect it, although doing so is necessary to take legal action against others who violate your copyright.
A trademark or service mark is a particular symbol, name, or phrase that identifies your business and helps consumers to recognize it. Your site's name may qualify as a service mark, for example, and the names of the products on your site may qualify as trademarks. In addition, if part of your site has a unique, distinctive appearance - a very recognizable graphic design, for example - then it may qualify for trademark protection, because that part of your site basically serves as "packaging" for your product or service
To protect your trademarks, conduct a search to ensure that your mark does not infringe on an existing one, and then register your trademark with the U.S. Patent and Trademark Office. This does not guarantee that no one will ever challenge your trademark, but it does strengthen your case if there is a problem.