That's an important point stated by Barry. Since you do not have a face-to-face interaction with customers, you definitely need to have a different mindset when dealing with customers online. Having a sole business online has it's own pros and cons. But if you are able to design a strategy around customer service, there's nothing much to worry about.
Since you or your customer doesn't see each other, building trust in the fist place can be a little tough. Therefore it's important to have every possible pointer at your business website which can help your prospect(s) build a certain level of confidence in you. Having a distinct contact no., address, email id. etc. can be useful. Having customer testimonials from your existing customers can further increase your chances of adding upto a customers confidence in you.
If you are a business that asks for customers personal data, it's vital to have those pages brought under SSL. An SSL plays a important role in the eyes of a customer by ensuring them that their data is being shared through an encrypted channel.
Actually, earning the trust of an online visitor needs a lot of dedication and research. Brainstorming can prove helpful attimes to understand the interest of your customer.