Just a thought,

   Perhaps, together with, or instead of cookie use, you could try something like

http://site.com/script.pl?sessid=encrypted_session_id or
http://site.com/encrypted_session_id in case of pathinfo use.

   This is of course linked to the session table on the server side.

I bet, that with a few snazzy math tricks, you can encode the current site state in that id, so you can use it for bookmarks.

-- Detonite