» Globex Designs | userstyles.org
I just started to use Stylish for Firefox and I must say that I love the Gmail & Gcal redesigns. I used greasemonkey years ago and thought it was a great add-on, but then I started to run into some issues with it so I stopped using it. Unlike Greasemonkey which uses Javascript to re-render a page; Stylish uses a CSS hack to accomplish this. I am not a serious coder, but it would make sense to me that the CSS approach is much lighter and probably runs into fewer problems than the javascript method. I am just assuming though so please don’t quote me on this.
Anyhow, try out Stylish. You will love it and it is super easy to use. You can also check out this Lifehacker article for additional Stylish Firefox hacks.