Greasemonkey is a super helpful utility Rated 5 out of 5 stars
This is the best EVER add on for firefox allowing you to customize the way that the browser behaves according to your needs and not according to all the unecesary things many sites shove down our browser.
Best scripts are at http://userscripts.org:8080/
Rated 5 out of 5 stars
This is the best mod ever for firefox and now for chrome allowing you to customize your browsing experience.
However 90% of the utility of the extension resides on the scripts and now that userscripts.org is dead
(see https://news.ycombinator.com/item?id=1574840), According to the site owner ( https://twitter.com/userscripts) there is a lack of useful scripts out there (unless you have the know how and time to make your own)
The only other option is
but it does not have nearly as many scripts as
userscript used to have.