var timelimits = 600000; // 10分钟
function check_session(){
	$.ajax({
		'url':'doajax.php?act=ajaxSetOnline',
		'type':'POST',
		'success':function(data){
			return true;
		}		
	});
	window.setTimeout( "check_session()", timelimits );
}//end
$(document).ready(function(){check_session();});