var req;

function retrieve(url,parameter) {
	if (window.XMLHttpRequest) { // Non-IE browsers
		req = new XMLHttpRequest();
		req.onreadystatechange = processStateChange;
		try {
			req.open("POST", url, true);
			req.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
		} catch (e) {
			alert(e);
		}
		req.send(parameter);
	} else if (window.ActiveXObject) { // IE
			req = new ActiveXObject("Microsoft.XMLHTTP");
			if (req) {
				req.onreadystatechange = processStateChange;
				req.open("POST", url, true);
				req.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
				req.send(parameter);
			}
		}
}
function processStateChange(){
	if (req.readyState == 4) { // Complete
		if (req.status == 200) { // OK response
				var m=req.responseText;
			//stopLoading();
			doSomething(m); // callback method
		} else {
			alert("Problem: " + req.statusText);
		}
	}
}