Firefox inside Firefox that mean 2 firefox in one frame. This is a funny and cool Firefox trick which would possibly amaze your accompany by embedding a Firefox window aural a Firefox window. Just type this code into your Firefox browser and hit enter:
chrome://browser/content/browser.xul

With the release of Firefox 3.0, Mozilla has an Easter Egg. Type “about:robots” in Firefox address bar and press Enter. It show a page having title as “Gort! Klaatu barada nikto!” with some pretty cool stuff.

Another firefox Easter Egg “The Book of Mozilla”, try typing “about:mozilla” on your firefox browser.