function getXMLHttpRequest() {

  var XHR = null, browserUtente = navigator.userAgent.toUpperCase();

  if(typeof(XMLHttpRequest) === "function" || typeof(XMLHttpRequest) === "object") {
    XHR = new XMLHttpRequest();
  } else if(window.ActiveXObject && browserUtente.indexOf("MSIE 4") < 0) {
    if(browserUtente.indexOf("MSIE 5") < 0) {
      XHR = new ActiveXObject("Msxml2.XMLHTTP");
    } else {
      XHR = new ActiveXObject("Microsoft.XMLHTTP");
    }
 }

 return XHR;
} 

function send (action, data, container) {
  var ajax = getXMLHttpRequest();
  ajax.open("post", action, true);
  ajax.setRequestHeader("content-type", "application/x-www-form-urlencoded");
  ajax.setRequestHeader("connection", "close");
  ajax.onreadystatechange = function() {
    if(ajax.readyState === 4) {
      if(ajax.status == 200) {
        document.getElementById(container).innerHTML = ajax.responseText;
      } else {
        alert("Operazione fallita, errore numero " + ajax.status);
      }
    }
  } 
  ajax.send(data); 
}