In Firefox it is possible to add extra functionality to web applications with extensions such as Greasemonkey and Stylish. Opera also has this feature natively. Which of these types of scripts do you find the most useful?
2 Answers
There's a script published on meta that hides the FAQ popup that appears when you first visit a StackExchange site.
Cookie Zapper can be useful for some sites, although it's lower-left status is annoying.