$sql=mysql_query("INSERT INTO admin_cont 
                  (contact_idemail , contact_timestamp , contact_objet , contact_message) 
                 VALUES 
                  ('".$_COOKIE['zzzzz']."', '$timestamp', '$objet', '$message' ") or die(mysql_error()); 

i hatayı almaya devam:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1

şerefe