var ajax = false;

if (window.XMLHttpRequest)
{
ajax = new XMLHttpRequest();
}
else if (window.ActiveXObject)
{
try {
	ajax = new ActiveXObject("Msxml2.XMLHTTP");
	} catch (e1) {
	try {
	ajax = new ActiveXObject("Microsoft.XMLHTTP");
	} catch (e2) { }
	}
	}
	
if (!ajax)
{
alert ("AJAX unavailable");
}