If you're not familiar with an online store, it's a good idea to contact them first and ask for some company background before you buy.
Most people are perfectly honest.
However, if you do have any problems, your legal rights may not be the same as they would be if you were dealing with a business. If you register with a particular store or site, you'll be asked to enter a user name and password. A good policy should cover the cost and method of delivery, the currency accepted and the taxes applied. It should also tell you the return and refund rules. Your browser is the piece of software that enables your computer to access the World Wide Web.