need info on double headed eagle..

From: gitaraghavan
Message: 12266
Date: 2002-02-04

HI,
I would like to know some facts about "double headed eagle" found in
many mideval flags of europe. I happened to see the same double headed
eagle on the bottom of a garland adorning one of the hindu gods
"Vishnu". Also i found the same figure in one russian coin. Can any
one throw some light on what this creature was supposed to stand
for???
Thanks