I have a major problem about the forum. I tried to add a mod called AJAX CHAT. I did what it told me but I didn't succeed. I don't know what to do now!!

On top of the board, it has an error message saying:

Code:

'CHANGING_PROFILE'    => 'Changing forum profile settings'[phpBB Debug] PHP Notice: in file /includes/functions.php on line 3824: Cannot modify header information - headers already sent by (output started at /language/en/common.php:856)
[phpBB Debug] PHP Notice: in file /includes/functions.php on line 3826: Cannot modify header information - headers already sent by (output started at /language/en/common.php:856)
[phpBB Debug] PHP Notice: in file /includes/functions.php on line 3827: Cannot modify header information - headers already sent by (output started at /language/en/common.php:856)
[phpBB Debug] PHP Notice: in file /includes/functions.php on line 3828: Cannot modify header information - headers already sent by (output started at /language/en/common.php:856)


I don't know what to do! Help me! Thanks!