You may have come across this before, I know I have…. you have a server running IIS 7 (for example on Windows 2008 R2, which is what my server is), and you want to add multiple sites with certificates without using a unique IP address for each one.
In later versions of IIS such as version 8, you can use Server Name Indication (SNI) right there in the GUI to set the host name to use when someone connects using https. This allows the server to use the same IP address and port (typically 443) for multiple certificates.