HttpSession question

["Jason Kretzer/STAR BASE Consulting Inc." <JKretzer@xxxxxxxxxxxxxxx>]

I have a question about the persistence
of a session.  Here is an example scenario:

User comes to my site(www.mySite.com)
and a session is created and some attributes are added to the session.
 The user then clicks a link to (www.theOtherSite.com).  The
user then does some stuff on the other site and clicks a link back to my
site.  

Questions:
1.) Is my original session object still
active?
2.) OR  Does the session get destroyed?
3.)  If the session is destroyed,
is there a way to get it back?

Separately:
4.)  How can session id's be used
in this instance? 

Note:  I can control the url string
on the other site to contain whatever I like at all times.


Thanks,

-Jason