Sessions

I am sending this again since I didn't get any response!! Hello, I am building a shopping cart using PHP and it uses sessions to manage and track users. I use URL to propagate the session ID. I am using codes like: <? require("include.php"); if($ID) session_id($ID); session_start(); if (!$PHPSESSID) { session_register('user'); session_register('auth'); } $cusession=session_id(); echo "To continue <A HREF=\"somepage.php?ID=$cusession\">click here</A>" ?> Now say someone comes to my site and has session ID of say 1234. So when he roams my site the address will be something like www.mydomain.com/page.php?ID=1234 . Now say he/she bookmarks this page and it will be bookmarked as www.mydomain.com/page.php?ID=1234 . Now say after few months another user comes to my site and gets the session ID of 1234 and at that time the earlier client with his bookmark logs in. At this time both will have the same session ID and will get all the variable of the other. How can I overcome this problem? Is there any better way to handle sessions? Any help will be appreciated. Thanks in advance. -Russell.