var g_baseUrl = "keepalive.php";
var reqAjax;

function enter() {
  var url = g_baseUrl;
  reqAjax = null;

  if (window.XMLHttpRequest) {
    reqAjax = new XMLHttpRequest();
  } else if (window.ActiveXObject) {
            reqAjax = new ActiveXObject("Microsoft.XMLHTTP");
  }
  if (reqAjax != null) {
    reqAjax.open("GET", url, true);
    reqAjax.send(null);
    setTimeout( "processApp()", 2000 );
  }
};
function processApp() {
  if (reqAjax.readyState == 4) {
    if (reqAjax.status == 200) {
      setTimeout( "enter()", 2000 );
    } else {
      alert("Can't retrieve XML: " + reqAjax.statusText);
    }
  } else {
    setTimeout( "enter()", 2000 );
  }
};