function createRequestObject() {

   var req;

   if(window.XMLHttpRequest && !(window.ActiveXObject)) {
      // Firefox, Safari, Opera...
      try {
          req = new XMLHttpRequest();
          } catch(e) {
          req = false;
      }
   } else if(window.ActiveXObject) {
      // Internet Explorer 5+
      try {
          req = new ActiveXObject("Msxml2.XMLHTTP");
          } catch(e) {
          try {
              req = new ActiveXObject("Microsoft.XMLHTTP");
              } catch(e) {
              req = false;
              }
          }
   } else {
      // There is an error creating the object,
      // just as an old browser is being used.
     alert("Your Browser Does Not Support This Script - Please Upgrade Your Browser ASAP");
   }

   return req;

}

// Make the XMLHttpRequest object
var http = createRequestObject();

function sendRequest(page) {

   // Open PHP script for requests
   http.open('get', page);
   http.onreadystatechange = handleResponse;
   http.send(null);

}

function handleResponse() {

   if(http.readyState == 4 && http.status == 200){

      // Text returned FROM the PHP script
      var response = http.responseText;

      if(response) {
         // UPDATE ajaxTest content
         document.getElementById("time").innerHTML = response;
      }

   }

}

function repeatloop()
{
sendRequest('time.php?sid='+Math.random()); // replace "inbox-status.php" with your php page's url
setTimeout("repeatloop()", 500);
}

window.onload=function() {
repeatloop();
}