Third party payment processors such as WorldPay and PayPal are used by eCommerce sites to provide secure credit card processing facilities.
Everything you ever wanted to know about taking paymentst via the internet can be found at the Online and Electronic Payment Solutions site.
WorldPay is perhaps the best known Payment Service Processor. WorldPay charge an £85 setup fee, £150 annual fee and take 4.5% of each transaction.
PayPal, which is a subsidiary of eBay, is another well known Payment Service Processor.