DevShed: Getting More Out of Apache (part 1)
January 5, 2001
"As you might imagine, the ability to host multiple Web sites on a single server is an elegant - and economical - solution to the problem of limited IP address range in the IPv4 protocol. It also allows Web hosting services to "sub-host" multiple client domains on a single server, and developers to run multiple Web sites on their development and test systems for simulation purposes."
"... Very simply, server-side includes are sets of instructions which enable Web servers to display data contained in server-side variables (server date and time, file currently in use, and so on). SSI also allows you to include external text files in your HTML pages - this comes in handy when you need to add a common header and footer to every HTML page."