Greasemonkey !! :), all might be wondering 😉 sounds very funny but what is it all about ?? 🙂 . Greasemonkey is a Firefox Addon which allows users to install userscripts , which can be used to change the look and functions of a webpage , analyze the data of the webpage and manipulate and display results based on the requirement of the users. These users are the regular visitors to that particular sites on which they would like to use this add-on.