function createXMLHttpRequest() {
	var http_request = false;
	
	if (window.XMLHttpRequest) {
		try {
			http_request = new XMLHttpRequest(); // Gecko (Firefox, Moz), KHTML (Konqueror, Safari), Opera, Internet Explorer 7
		}
		catch(e) {
			http_request = false;
		}
	}
	else if(window.ActiveXObject) {
		try {
			http_request = new ActiveXObject("MSXML2.XMLHTTP"); // Internet Explorer 6 
		} 
		catch(e) {
			http_request = new ActiveXObject("Microsoft.XMLHTTP"); // Internet Explorer 4,5 
		}
	} 
	   
	//Ci si assicura che l'header contenga text/xml
	if (http_request.overrideMimeType) {
		http_request.overrideMimeType('text/xml');
	}

	if (!http_request) {
		alert('Istanza XMLHTTP non generata');
	}

	return http_request;
}