It is time you know about Greasemonkey, if you haven’t heard about it already. Greasemonkey is a Firefox extension that lets you add bits of DHTML (“user scripts”) to any webpage to change its behavior. In much the same way that user CSS lets you take control of a webpage’s style, user scripts let you easily control any aspect of a webpage’s design or interaction.
Greasemonkey Firefox Extension
CNET reports
“That capability has gained the extension an avid following of Web surfers who want to customize the sites they visit, removing design glitches and stripping sites of ads. But the extension comes with substantial security risks and could stir trouble among site owners who object to individual, custom redesigns of their pages.”
Website designers do allow surfers to modulate the site to some extent like link colors and font size, but Greasemonkey goes much beyond that. Now users can fix bugs modulate and manipulate sites, remove ads, and much more from sites. See how Adrian Holovaty fixed a bug in Bloglines, using Greasemonkey and one line of JavaScript,
Greasemonkey scripts can perform a host of tasks on multiple websites according to the GreaseMonkey UserScripts page. You can install scripts by right-clicking on links to them and selecting “Install User Script…”. Or, you can select the same option under the tools menu while viewing the contents of a user script file. Also, you can write your own userscript with just a few steps. If you cant make it, then request it and other technical wizards might make it for you.