function getHttpRequest() {
   
    var xmlhttp = null;
    // Mozilla
    if (window.XMLHttpRequest) {
        xmlhttp = new XMLHttpRequest();
    }
    // IE
    else if (window.ActiveXObject) {
        xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    
    return(xmlhttp);
} 

function sendAjaxRequest(url)
{
  xmlhttp = getHttpRequest();
  xmlhttp.open("GET", url, true);
  xmlhttp.onreadystatechange = function() {
    if(xmlhttp.readyState != 4) {
    
    }
    if(xmlhttp.readyState == 4) {
      
    }
  }
  xmlhttp.send(null);
}