var http_request = false;

function makeRequest(url, parameters) {
   http_request = false;
    if (window.ActiveXObject) // IE
    { 
      try
      {
        http_request = new ActiveXObject("Microsoft.XMLHTTP");
      } 
      catch (e) {}
    }
   else if (window.XMLHttpRequest) { // Mozilla, Safari,...
      http_request = new XMLHttpRequest();
      if (http_request.overrideMimeType) {
         http_request.overrideMimeType("text/xml");
      }

   } 
   if (!http_request) {
      alert('Cannot create XMLHTTP instance');
      return false;
   }
   else
   {
        http_request.onreadystatechange = setContents;
        http_request.open('GET', url + parameters, true);
        http_request.send(null);
   }
}

function setContents() {
    if (http_request.readyState == 4)
    {
        document.getElementById("txtSubCategory").innerHTML = http_request.responseText;
    } 
   return true;
}