Greasemonkey is a Firefox extension that allows you to write scripts that alter the web pages you visit. You can use it to make a website more readable or more usable. You can fix bugs that the site owner can’t be bothered to fix themselves. You can alter pages so they work better with assistive technologies that speak to a web page aloud or convert it to Braille. You can even automatically retrieve data from other sites to make two sites more interconnected.
Link: O'Reilly Network
