note 54176 added to function.session-start

I got this warning on my script: "Warning: session_start(): Cannot send session cookie - headers already sent by (output started at /home/nyenius/public_html/forum/index.php:1) in /home/nyenius/public_html/forum/index.php on line 2" and when i try to login, the session don't want to register. What kind of error is that? ---- Manual Page -- http://www.php.net/manual/en/function.session-start.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+54176 Delete: added to the manual -- http://master.php.net/manage/user-notes.php?action=delete+54176&report=yes&reason=added+to+the+manual Delete: bad code -- http://master.php.net/manage/user-notes.php?action=delete+54176&report=yes&reason=bad+code Delete: spam -- http://master.php.net/manage/user-notes.php?action=delete+54176&report=yes&reason=spam Delete: useless -- http://master.php.net/manage/user-notes.php?action=delete+54176&report=yes&reason=useless Delete: non-english -- http://master.php.net/manage/user-notes.php?action=delete+54176&report=yes&reason=non-english Delete: other reasons -- http://master.php.net/manage/user-notes.php?action=delete+54176&report=yes Reject -- http://master.php.net/manage/user-notes.php?action=reject+54176&report=yes Search -- http://master.php.net/manage/user-notes.php