function getXMLHTTP() {
  var xmlhttp = false;
  if (window.XMLHttpRequest) {
    xmlhttp = new XMLHttpRequest();
  } else if (window.ActiveXObject) {
    try {
      xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
    } catch (e) {
      try {
        xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
      } catch (e) {
        xmlhttp = false;
      }
    }
  }
  return xmlhttp;
}

function ajaxRequest(url) {
  var request = getXMLHTTP();
  if (request) {
    request.onreadystatechange = function() {
      parseResponse(request);
    };
    request.open('GET', url, true);
    request.send(null);
  }
}

function parseResponse(request) {
  if (request.readyState == 4) {
    if (request.status == 200 || request.status == 304) {
      eval(request.responseText);
    }
  }
}