Someweb hosting companies share SSL certificates among websites on a server, but this often means that the websites will have problems running the security protocols. Because of how the internet works, there is no way for an online customer to know exactly who they are dealing with when they make purchases online. Problems have to be taken care of over the internet, and customers would much rather be assured that they wont have to do that.
Websites that useSSL certificates have a better chance of growing their business, because customers who trust are customers who come back and make additional purchases. The security based on SSL begins at the browser, which encrypts anything that is going to be sent to the server, where the website is based. The keys used to encrypt can be 40-bit or 128-bit. The 128-bit is more secure simply because a longer key is more difficult to decrypt, but sometimes 40-bit has to be used, such as if the server on the other end of the line of communication can only decrypt 40-bit security keys.
To get an SSl certificate, website owners submit a Certificate Signing Request, which is reviewed by a certificate authority before a website is given a server certificate. They can also begin the process through their web hosting company, if they have one. After the certificate authority approves things, the certificate can be installed and used.