var request = false;

try {
	request = new XMLHttpRequest();
} catch (trymicrosoft) {

	try {
		request = new ActiveXObject("Msxml2.XMLHTTP");
	} catch (othermicrosoft) {

		try {
			request = new ActiveXObject("Microsoft.XMLHTTP");
		} catch (failed) {
			request = false;
		}
	}
}

if (!request)
	alert("Error initializing XMLHttpRequest!");