Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent

Problem :
warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/content/76/8154676/html/admin/index_action.php:2) in /home/content/76/8154676/html/admin/index_action.php on line 2

solution:

1) Remove white spaces
2) session start on 1st line after <?php
3) encoding utf8 without bom
4)ob_gzhandler and ob_start()
5)@session_start();