simple questions about sessions

Hi! 1- is there a way with which i can verify that a session variable is registered or exists without using start_session cause if it's not registered and there is no session it'll create the session ! i tried isset() but if it's set i have to use start_session so as to get the values and as we know start_session should be at the beginning! 2- if i create a session in a page can it be used in all the site pages and rames without adding any $phpsessid to all urls? in my php.ini the enable-transit-id is enabled ! byt the way what do u mean by compilin php? i just save the php.ini! 3-with IE and netscape as i add the phpsessid to urls , sometimes it remmbers an old session and displays it to me ! how can i avoid these? please help i'm confused! _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.