Firefox 3 has two (maybe more) easter eggs in it.

In the address bar, type  about:mozilla and about:robots to find somethin quirky..

about:mozilla

Mammon slept. And the beast reborn spread over the earth and its numbers grew legion. And they proclaimed the times and sacrificed crops unto the fire, with the cunning of foxes. And they built a new world in their own image as promised by the  sacred words, and spoke of the beast with their children. Mammon awoke, and lo! it was caught but a follower.

from The Book of Mozilla, 11:9
(10th Edition)

about:robots

# Robots may not injure a human being or, through inaction, allow a human being to come to harm.

#             Robots have seen things you people wouldn’t believe.

#             Robots are Your Plastic Pal Who’s Fun To Be With.

#             Robots have shiny metal posteriors which should not be bitten.