problem when mixing session in PHP with ajax

[szpilman]

dear all,
i just start my way to learn AJAX
i am using a simple framework
AJAXGOLD.JS

i am tryin to make an application that combine the use of AJAX with session in PHP. but i got this message, when i do the 'session'-ing
this is the warning.

Warning: 
Cannot send session cache limiter - headers already sent 
(output started at c:\apache\htdocs\ajax\lat2_ajaxgold\chat.php:3) in
c:\apache\htdocs\ajax\lat2_ajaxgold\chat.php on line 6

if there is any idea of how to handle session + AJAX,
or give the links, i'd be very thankful

rgrds,

szpilman