Basic Ajax...

ajax.js

function ajax(url) {

  try {
    xmlhttp = window.XMLHttpRequest?new XMLHttpRequest(): new ActiveXObject("Microsoft.XMLHTTP");
  } catch (e) {
    // browser doesn't support ajax. handle however you want
  }

  xmlhttp.onreadystatechange = triggered;
  xmlhttp.open("GET", url);
  xmlhttp.send(null);
}

function triggered() {
  if ((xmlhttp.readyState == 4) && (xmlhttp.status == 200)) {
    document.getElementById("output").innerHTML = xmlhttp.reponseText;
  }
}