Certificate Authority

A Certificate Authority issues the SSL certificate. There are many CA's you can purchase from at a variety of prices. Unfortunately they are not all equal. If you buy your SSL certificate from a relatively unknown CA then people may encounter warning messages on their browser as they navigate the https pages of your website. A browser usually has a limited number of root Certificate Authorities that it trusts. A certificate that isn't signed by one these trusted autorities or a certificate that is "chained" from a relatively unknown CA can cause grief.

When deciding which SSL certificate to purchase you need to consider who will be buying from you.  If you are planning to reach the majority of people but don't care if you miss out on a few sales because someone has an older computer then just buy a cheaper certificate. You can often find them offered by your hosting company or the place you buy domains from.Some web hosts allow you to purchase a certifiacte directly from them and will even install it for you. This is often a good option because unless you are a technical person it could be a daunting task to figure out how to install the certificate.

If you want to capture more sales then consider buying a certificate from an older trusted CA like Thawte. Finally if you are dealing with very sensitive information like a bank does then you may decide to get a top of the line SSL certificate from a well known Certificate Authority like Thawte or VeriSign.