Unexpected Session Behavior on Mozilla

Hello PHP-DB listers, I've a PHP, MySQL Web Page script that branches according to browser (e.g., MSIE, or Mozilla ) and which uses a small number of session variables. I've noticed that when connecting through Explorer, for each browser / page instance opened on the same machine, there is a new session file created ( as I would expect ). Yet when connecting through Mozilla on RH9, there is only one session file created per machine, which causes a second instance of the page to inherit the values of the session variables from the previously opened page. This is confusing to me, to say the least. Anybody have any thoughts as to why this is occurring? MySQL 4.0.16 PHP 4.3.4 Apache 2.0.48 Win2K IE 5.50x RH9 Mozilla 1.2.1 Dave