if (typeof XMLHttpRequest == "undefined")
  XMLHttpRequest = function() 
  {
    try { return new ActiveXObject("Msxml2.XMLHTTP.6.0"); } catch(e) {};
    try { return new ActiveXObject("Msxml2.XMLHTTP.3.0"); } catch(e) {};
    try { return new ActiveXObject("Msxml2.XMLHTTP"); }     catch(e) {};
    try { return new ActiveXObject("Microsoft.XMLHTTP"); }  catch(e) {};
    
    throw new Error("This browser does not support XMLHttpRequest or XMLHTTP.");
  };

function ajax(url, vars, callbackFunction)
{
  var request =  new XMLHttpRequest();
  request.setRequestHeader("Content-Type",
                           "application/x-javascript;");
 
  request.onreadystatechange = function()
  {
    if (request.readyState == 4 && request.status == 200)
    {
      if (request.responseText)
      {
        callbackFunction(request.responseText);
      }
      else
      {
        callbackFunction();
      }
    }
  };

  request.open("POST", url, true);
  request.send(vars);
}