And so at last the beast fell and the unbelievers rejoiced. But all was not lost, for from the ash rose a great bird. The bird gazed down upon the unbelievers and cast fire and thunder upon them. For the beast had been reborn with its strength renewed, and the followers of Mammon cowered in horror.
from The Book of Mozilla, 7:15
Type about:mozila into your Firefox address bar and you will get this "easter egg". Of course, Mammon refers to MS IE. For the interpretation of the above "holy text", please refer to Wikipedia.
Some other tricks in Firefox:
about:config, about:buildconfig, about:cache, about:plugins, about:credits, about:mozilla