function changeTab(tid) {
	var xmlHttp3 = createxmlHttp();
	var obj = fetch_object('tabcontent');
	var url = "ajax_tab.php?do=tab_"+tid;
	xmlHttp3.open("GET",url);
		xmlHttp3.onreadystatechange = function(){
			if(xmlHttp3.readyState == 1 || xmlHttp3.readyState == 2){
				obj.innerHTML = '<center><img border="0" src="images/loading.gif"></center>';
			}
			else if(xmlHttp3.readyState == 4 && xmlHttp3.status == 200){
				var response = xmlHttp3.responseText;
				obj.innerHTML = response;
			}
		}
	xmlHttp3.send(null);
}