Just after you thought you knew the details of Google..

[Subbarao Kambhampati <rao@asu.edu>]

In its latest makeover, Google also tweaked the closely guarded formula
that determines which Web sites are most relevant to a search request.

Google has made five significant changes to its algorithmic formulas in
the last two weeks, Brin said. 

http://www.cnn.com/2004/TECH/internet/02/18/google.expands.ap/index.html

Rao

ps: Extra Credit Homework Problem: Find out what the five significant
changes are