The remaining purchases are made using snail-mailed checks or other payment processing services.

And while the latter does give consumers a small measure of comfort because they don't have to enter their card number and expiration date, they lose the built-in buyer protection programs offered by most cards. And that can cause some anxiety as they can't hold and inspect an online purchase until it arrives at their home.

Nonetheless, the numbers are yet one more piece of evidence that e-merchants looking to grow their business are better served by having credit card processing services on their sites. However, prospective Web store owners need to choose their card processing provider with care, taking into account a host of factors. Not all providers are the same.

First, and this seems to top just about everybody's list, is the matter of price. What are the costs going to be associated with adding processing services into your business? There is no simple answer to this question.

There are typically fees connected to starting up, monthly fees and per-transaction fees, among other costs associated with card processing. However, not all companies levy the same amounts. This is where doing some Web surfing will pay dividends.

Take some time and look at several sites. The reputable companies will have their fee schedules on display, which means you can do a side-by-side comparison based on the dollars involved. But it's not all about the money.

Your next consideration needs to be service and support. One way to weed out the bad from the good is to investigate their service/support policies and reputation. First, do they offer 24/7 coverage? Your business is going to be available all day, every day, and the company processing those transactions shouldn't have down time.

And are their support people within the company, or is it outsourced? If they're inside the company that's an advantage because all they deal with is the system you're using. And while you're asking, how fast is their response time, because this is a case where time literally is money. You can't afford to stay on hold while potential purchases are being moving over to the competition.

One other area of concern is do they charge for service calls, or is it part of the package? You shouldn't have to think twice before you ask for help, and not calling on a small problem creates the possibility it could grow into a big problem.

And finally – and this applies to everything already mentioned – don't be shy about asking questions if there are things you don't understand. And ask as many as it takes to get the answers you need.

A good company will answer every single one of them, which demonstrates good service before the sale. Indeed, red flag any company that gets testy or evasive with your questions. At worst, it means they have something to hide. At best it could be a sign of how poorly you'll be treated as a customer.