//Ajax caller, generic
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('Some functionality is unavailable');
}