Last URL

["Steven Lee" <blindeagle@xxxxxxxxxxxx>]

Dear all:

I try to write a logging page which can know how the users find my site.
if by search engine or some banner switch, they must from another site
(yahoo,xxx.com etc.)
I try to find it in $HTTP_SERVER_VARS[], seems no, I am not sure.
Is ther any Possible way that I can know what is the last URL before the
user get into my site?


Thank you

Steven