function GetXmlHttpObject() { 
  var objXMLHttp=null;
  if (window.XMLHttpRequest){
    objXMLHttp=new XMLHttpRequest();
  } else if (window.ActiveXObject) {
    objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
  return objXMLHttp;
} 

function lit_excursion (id, lang) {
  xmlHttp=GetXmlHttpObject();
  url="/httpExcursion.php?id="+id+"&lang="+lang;
  xmlHttp.onreadystatechange=function () {
    if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete") { 
      div_excursion = document.getElementById ("divD111");
      div_excursion.innerHTML = xmlHttp.responseText;
      // ...
    }
  }
  xmlHttp.open("GET",url,true);
  xmlHttp.send(null);        
}