Include()

Hi,

I would like to include punbb to my homepage but i've come across on problem. i don't know how to inlude it. I try white code...

<?php
include("forum/index.php");
?>

and code returns

Warning: main(./include/common.php): failed to open stream: No such file or directory in /var/www/localhost/htdocs/users/bizon/forum/index.php on line 27

Fatal error: main(): Failed opening required './include/common.php' (include_path='.:/usr/lib/php') in /var/www/localhost/htdocs/users/bizon/forum/index.php on line 27

what is wrong? (please be exact because i'm php beginner)

thx for the answers.