Visiting launchpad.net in browser causes icon to appear in launcher, how do I remove it?

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http://askubuntu.com – Using Ubuntu 12.10 with Unity. I think I agreed to install a Launchpad add-on in Firefox the first time I visited the site (launchpad.net), and ever since then, whenever I have an open tab in Firefox with any page on launchpad.net loaded, an icon appears in my Launcher desktop widget. If I right-click on the icon and select quit, it also closes the tab in Firefox. I've since uninstalled the Firefox add-on and rebooted, and it's still happening. How do I make it stop? It's so annoying Screenshot: (HowTos)