Facebook Page Plugin

When I add the facebook plugin code into the index.php file a warning starts to appear on the home page:

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/forte617/public_html/sitefortec/index.php:16) in /home/forte617/public_html/sitefortec/libraries/joomla/session/session.php on line 665

My website is: http://fortecdigital.com.br/sitefortec/

Hi,
sorry but we do not support php/html code customizations,
if you were smart you wouldn't touch template core files,
all Joomla plugins request only INSTALLATION in admin.
--that's all--