var index=''
			var http_request = false;
			function selccenter(pid)
			{
				index=document.all('centers');
				url='index1.php?req=centerslist&pid='+pid;
				if (pid == 0) {
					index.innerHTML = '';
					return;
				}
				http_request = false;
				if (window.XMLHttpRequest){ // Mozilla, Safari,...
					http_request = new XMLHttpRequest();
					if (http_request.overrideMimeType) {
						http_request.overrideMimeType('text/xml');
					}
				}
				else if (window.ActiveXObject){ // IE
					try {
						http_request = new ActiveXObject("Msxml2.XMLHTTP");
					}
					catch (e){
						try {
							http_request = new ActiveXObject("Microsoft.XMLHTTP");
							}
							catch (e) {}
					}
				}
			
				if (!http_request){
					alert('Giving up :( Cannot create an XMLHTTP instance');
					return false;
				}
				http_request.onreadystatechange = alertContents;
				http_request.open('GET', url, true);
				http_request.send(null);
			}
			
			function alertContents()
			{
				if (http_request.readyState == 4){
					if (http_request.status == 200){
						index.innerHTML=http_request.responseText;
					}
					else{
						alert('There was a problem with the request.');
						}
				}
			}