Restyle the web with Stylish, a user styles manager. Stylish lets you easily install themes and skins for Google, Facebook, YouTube, Orkut, and many, many other sites. You can even customize Firefox and other programs themselves.
Show the IP address(es) of the current page in the status bar. It also allows querying custom information services by IP (right click) and hostname (left click), like whois, netcraft, etc. Additionally you can copy the IP address to the clipboard.
It adds a tab to the Page Info dialog box, which shows the cookies belonging to the current page.
View Dependencies adds a tab to the Page Info window, in which it lists all the files which were loaded to show the current page.