sessions and cookies

I am using sessions to password protect a section of a website. I am storing the session ID in a cookie but just in case cookies are not enabled, I am also passing the session ID in the query string to each page in the protected directory. Please can someone tell me if this could cause any problems, especially if the user if tries to access a URL from their history bar in the browser with an old session ID. i think what I'm trying to ask is , if the script receives a session ID from a query string and cookie, which does it use ? Thanks, David. ----------------------- Fed202 Solutions www.fed202solutions.com Mobile : 07779 293368 -----------------------