I'm looking for an extension what will apply a specific stylesheets to specific websites. For example googlestyle.css
would go with Google.com and superuserstyle.css
would go with superuser.com.
Firefox – Custom Per-Site Stylesheet Extension
browser-addonscssfirefox
Best Answer
I believe you're looking for Stylish. (official addon page)
(Despite the above, it's just as easy to use your own stylesheets for any website).