customize any webpage using GREASEMONKEY

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 web site more readable or more usable. You can fix rendering bugs that the site owner can't be bothered to fix themselves. You can alter pages so they work better with assistive technologies. You can even automatically retrieve data from other sites to make two sites more interconnected.

Greasemonkey by itself does none of these things. In fact, after you install it, you won't notice any change at all... until you start installing what are called “user scripts”. A user script is just a chunk of Javascript code, with some additional information that tells Greasemonkey where and when it should be run. Each user script can target a specific page, a specific site, or a group of sites. A user script can do anything you can do in Javascript. In fact, it can do even more than that, because Greasemonkey provides special functions that are only available to user scripts.

here are the links for every thing related to greasemokey:
GREASEMONKEY DOWNLOAD LINK
SCRIPT REPOSITORY
WEBLOG OF GRESEMONKEY
USERSCRIPT

There is also online tutorials to write your scripts . There is an ebook (diveintogreasemonkey) that i have uploded in MY BOX(widget on right side of the page), which might be of intrest if you want to code your own scripts.