Server Side Includes (SSI) is a simple server-side language, which allows you to incorporate text from a specific source inside a web page. In the most typical case, the text from a file is integrated in a different one, giving a site the feeling it is dynamic. For instance, if your site is comprised of 10 web pages, 5 of them can include the content of any kind of file, such as horoscope.txt. As soon as you alter this text file, the new content will come up on all five web pages, which will enable you to update your site much easier than if you had to change part of all 5 web pages. Server Side Includes is at times utilized to incorporate the output of simple commands, scripts or functions as well - a hit counter that's shown on the site, the current time and date or the visitor's IP address. Every webpage that makes use of SSI should have a unique extension - .shtml.