Can't press back in Session

[hkjeffrey]

Hello,

I've registered a session after checking username and password. Then all pages have start_session(). After I've displayed something from a search page, I pressed "Back" button on the broswer. The data in the previous page can't be displayed (it said:"The session is expired ....."). How can I fix it wihout removing the session_start()? As I don't want others to view any page without logged in.

Thank you so much!!

[hkjeffrey]

Sorry, here is the outline of my phps:
index.html (html form) -> selection.php (session_register('id') and html form) -> result.php (session_start() and a query link to another php) -> details.php (session_start(), html form).

And, I want to press "Back" in details.php and want to see other results in result.php. But, it displayed "session expired ....."

Please Help!! Many thanks!!