Server Side Includes (SSI) is a basic server-side language, which allows you to incorporate text from a specific source in a web page. In the most typical scenario, the text from a file is incorporated in another, providing a website the sense that it's dynamic. For example, if your website involves ten pages, 5 of them can easily contain the content of any kind of file, such as horoscope.txt. Any time you modify this text file, the modified content will come up on all five webpages, which shall let you revise your site much easier than if you had to modify part of all five web pages. Server Side Includes is sometimes employed to incorporate the output of basic commands, scripts or functions as well - a hit counter that is displayed on the site, the current date and time or the visitor's IP address. Every web page that works by using SSI should have a unique extension - .shtml.
