<script language="javascript" type="text/javascript">
<!--
//Browser Support Code
function ajaxUpUp(){
     // Basically determines what browser the viewer is using
     var ajaxRequest;

     try{
          ajaxRequest = new XMLHttpRequest();
     } catch (e){
          try{
               ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
          } catch (e) {
               try{
                    ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
               } catch (e){
                    alert("Error");
                    return false;
               }
          }
     }
     // Create a function that will receive data sent from the server
     ajaxRequest.onreadystatechange = function(){
          if(ajaxRequest.readyState == 4){
               var ajaxDisplay = document.getElementById('ajaxDiv');
               ajaxDisplay.innerHTML = ajaxRequest.responseText;
          }
     }
     ajaxRequest.open("GET", "test.php", true);
     ajaxRequest.send(null);
}
// Refreshes the above code every 1 second
setInterval('ajaxUpUp()', 1000);
//-->
</script>

onload="ajaxReadChat()"

<div id="ajaxDiv"></div>