Server Side Includes (SSI) is a simple server-side language, which lets you include text from a given source in a web page. In the most widespread scenario, the text from a file is integrated in another, providing a site the feeling that it is dynamic. For instance, if your site comprises of ten web pages, five of them can contain the content of any kind of file, like horoscope.txt. As soon as you modify this text file, the new content will appear on all of the five pages, which will allow you to revise your site much easier than if you had to update a component of all 5 web pages. Server Side Includes is in some cases employed to incorporate the output of simple commands, scripts or functions as well - a hit counter that is displayed on the website, the present date and time or the visitor's IP address. Any webpage that uses SSI should have a particular extension - .shtml.