Say, you use cookie(not URL rewriting) to implement session control, but your client browser is so alert that it will decline all the cookies sent by any server. In such a case, your client will choose NOT to join the session. Hope this can help.
SCJP 1.2 (88%)<br />SCWCD 1.4 (89%)<br />SCBCD (in progress)<br />SCEA (in progress)