function affichage(str)
{ 
xmlHttp=GetXmlHttpObject() ;
if (xmlHttp==null)
{
  alert ("Browser does not support HTTP Request")
  return
}
  var url="clas2.php" ;
  url=url+"?q="+str ;
  //url=url+"&sid="+Math.random()
  xmlHttp.onreadystatechange=stateChanged ;
  xmlHttp.open("GET",url,true);
  xmlHttp.send(null)
}

function stateChanged() 
{ 
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
   { 
    document.getElementById("reponse").innerHTML=xmlHttp.responseText;
   } 
} 

function GetXmlHttpObject()
{
  var xmlHttp=null;
  try
    {
    // Firefox, Opera 8.0+, Safari
    xmlHttp=new XMLHttpRequest();
    }
  catch (e)
    {
    // Internet Explorer
    try
      {
      xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
      }
    catch (e)
      {
      xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
    }
  return xmlHttp;
}