Hi Chris,
your code is accurate yes - and the person would be "logged out".
Pressing back will trigger a GET or POST to the server, and this GET/POST will obviously have a sessionId (since the original did). So at this point a _new_ session is started, albeit one with the same numebr as before.
At this point the user is still logged out - and a new session is underway.
This is why it's so important to make sure that every window that _requires_ the person to be logged in actually has the "must be logged in" switch set.
It's of course, not just the "back" button that creates the risk here - the user can type in the URL at any time they like, and the same issue applies.
Cheers
Bruce