var xhr = null; 
function getXhr(){
	if(window.XMLHttpRequest){ // Firefox and others
	   xhr = new XMLHttpRequest(); 
	}
	else if(window.ActiveXObject){ // Internet Explorer 
	   try {
				xhr = new ActiveXObject("Msxml2.XMLHTTP");
			} catch (e) {
				xhr = new ActiveXObject("Microsoft.XMLHTTP");
			}
	}
	else {
	   alert("Your browser does not support XMLHTTPRequest object"); 
	   xhr = false; 
	} 
}