// check is username is already in use by another user
function checkUser() {
  var u = document.getElementById("username").value;
  var oXmlHttp = zXmlHttp.createRequest();
  oXmlHttp.open("get", "../profile/checkUser.aspx?id=" + u, true);
  oXmlHttp.onreadystatechange = function () {
    if (oXmlHttp.readyState == 4) {
      if (oXmlHttp.status == 200) {
        var dn = document.getElementById('dupName');
        if (oXmlHttp.responseText == "stop") {  
          dn.style.display = "";
        }
        else {
          dn.style.display = "none";
        }
      }
    }
  }
  oXmlHttp.send(null);
}