Server Side Includes (SSI) is a simple server-side language, which allows you to include text from a specified source within a web page. In the most popular case, the text from a file is integrated in a second one, providing a site the feeling it is dynamic. For instance, in case your website is comprised of ten pages, five of them can include the content of some file, for example horoscope.txt. Any time you alter this text file, the new content will come up on all five web pages, which shall permit you to revise your site much easier than if you had to update part of all 5 web pages. Server Side Includes is at times employed to contain the output of simple commands, scripts or functions as well - a hit counter that's shown on the website, the present date and time or the visitor's IP address. Every web page that employs SSI should have a particular extension - .shtml.