SSI (Server Side Includes) is a server-side scripting language. It is used to include the contents of one or more files into a web page in the web server. It is useful in including a common piece of code such as a page header, a page footer and a navigation menu. It includes PERL language-based commands for gathering information from the server. Most Linux servers run SSI and WindowsNT servers have to go with ASP. SSI is often used to simplify the maintenance of a website.