User script
From GreaseSpot Wiki
User scripts, or userscripts, are scripts that make on-the-fly changes to specific web pages on the client side (in the browser or a proxy server), typically to change their appearance or to add or modify functionality.
User scripts for Greasemonkey and Greasemonkey-compatible alternatives are written in JavaScript, but there is at least one example of using another scripting language, namely Ruby in MouseHole.
//For tools other than Greasemonkey that apply user scripts to web sites, see Cross-browser Userscripting and Wikipedia. Media:Example.ogg
