Server Side Includes (SSI) is a simple server-side language, which enables you to incorporate text from a specific source inside a web page. In the most widespread situation, the text from a file is integrated in a second one, providing a site the sense that it is dynamic. As an example, in case your site is made of ten web pages, five of them can easily have the content of any kind of file, such as horoscope.txt. In case you modify this text file, the modified content is going to appear on all of the five webpages, which shall allow you to update your site faster and easier than if you had to modify a part of all five pages. Server Side Includes is sometimes employed to include the output of basic commands, scripts or functions as well - a hit counter that is shown on the site, the present time and date or the customer's IP address. Every webpage that makes use of SSI will need to have a unique extension - .shtml.