Session ID problem (?)

I am working with sessions, which I don't have too much experience with
(yet). In trying to make sure my logout code works correctly, I am printing
the session ID on each page I visit, before and after I log the user out. I
have an index.html page which allows users to login or register. When they
register, I put cookies on their machine to make it easier to log them in
the next time they visit. When they login after the cookies are placed on
their machines, the code automatically skips the login form and goes
straight to the content the site provides. The problem seems to be that two
separate session IDs are created, one by the "home" page (NOT index.html)
and one by the remaining pages. Below is a trace of the pages I'm visiting
in my test, with the session IDs associated with each.

INDEX.HTML
LOGIN.JSP Session ID : czyf9dp7.224f
<<< LoginServlet >>>
HOME.JSP Session ID : czyf9dp7.e83 (*)
SETTINGS.JSP Session ID : czyf9dp7.224f
FAQ.JSP Session ID : czyf9dp7.224f
CONTACT.JSP Session ID : czyf9dp7.224f
HOME.JSP Session ID : czyf9dp7.224f (#)
LOGOUT.JSP Session ID : czyf9dp7.224f

< old session was invalidated here >

INDEX.HTML
LOGIN.JSP Session ID : czyf9dp7.6a03
<<< LoginServlet >>>
HOME.JSP Session ID : czyf9dp7.72a9 (*)
SETTINGS.JSP Session ID : czyf9dp7.6a03
FAQ.JSP Session ID : czyf9dp7.6a03
CONTACT.JSP Session ID : czyf9dp7.6a03
HOME.JSP Session ID : czyf9dp7.6a03 (#)

What's really odd is that the first time the home.jsp page is visited (*),
it's ID is different from the others, but the second time (#) it matches.

Each JSP has the session page directive set to true. Also, the code that
checks the login information is a servlet.

Any ideas?
Bob