function ajax(url, f, a) {
	var xmlHttp;
	try { // Firefox, Opera 8.0+, Safari
		xmlHttp = new XMLHttpRequest();
	}
	catch (e) { // Internet Explorer
		try {
			xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
		}
		catch (e) {
			try {
				xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
			}
			catch (e) {
				alert("Your browser does not support AJAX!");
				return false;
			}
		}
	}
	if (f) {
		xmlHttp.onreadystatechange = function() {
			if (xmlHttp.readyState == 4 && xmlHttp.status == 200)
				f(xmlHttp.responseText, a);
		};
		xmlHttp.open("GET", url, true);
		xmlHttp.send(null);
	}
	else {
		xmlHttp.open("GET", url, false);
		xmlHttp.send(null);
		return xmlHttp.responseText;
	}
}