Fun with Firefox URLs

Firefox’s user interface is written using XUL and Javascript. The Gecko engine which renders the webpages also renders the user interface. This means you can enter chrome URLs into the Firefox address bar and do some really cool things.

chrome://browser/content/browser.xul

This is awesome. Type this in the address bar and you can have a nested copy of Firefox running inside Firefox. You can even open up several tabs at this URL and have tabbed windows. You can even nest Firefox inside itself several times. Most things seem to work.