Server Side Includes

A server-side include is a function performed by a web server that embeds ('includes') information into the middle of an HTML file as it's being sent to the web client.

This is convenient for inserting the current time or a file's size into your HTML document without resorting to writing a CGI. It is also useful for placing common headers and footers (such as copyright notices, addresses, and other boilerplate items) on a set of pages.