If you are running an e-commerce business, you need to secure transactions between your customers and your site. To prevent the valuable data, such as credit card numbers and other personally identifiable information from stealing, you should use the Secure Sockets Layer protocol, which encrypts all data and transfers them securely over the SSL connection. And even if someone intercepts the data for malicious intent, they will not be able to decrypt and use them.
To implement the Secure Sockets Layer protocol on your web server, you should purchase an SSL certificate from a reputable certificate vendor (these vendors are called Certificate Authorities), and then install this certificate on your site. To enable SSL protection, you must host your site on a dedicated IP address, which is not shared among other web sites.
There are numerous certificate authorities to choose from. When considering one, pay attention to reputation and credibility of the CA. Knowing how long they have been in business and how many customers they have will help you make the right choice.
Your Parallels Plesk Panel provides facilities for purchasing SSL certificates from Comodo, GeoTrust, Inc and GoDaddy.