This script I wrote works perfect on IE! It works on Chrome and FireFox the first time you do an action but it fails on the rest.

The script is simple. You can Add or Delete a user and each time you Add or Delete a user it updates the Updates the list.

Code:
<script type="text/javascript">

function Add() {
  http_request = false;
  cache=Math.random();
  var username=document.getElementById('username').value;
  if (window.XMLHttpRequest) { // Mozilla, Safari,...
      http_request = new XMLHttpRequest();
      if (http_request.overrideMimeType) {
        http_request.overrideMimeType('text/html');
      }
  } else if (window.ActiveXObject) { // IE
      try {
        http_request = new ActiveXObject("Msxml2.XMLHTTP");
      } catch (e) {
        try {
            http_request = new ActiveXObject("Microsoft.XMLHTTP");
        } catch (e) {}
      }
  }
  if (!http_request) {
      return false;
  }
  http_request.onreadystatechange=function(){ if (http_request.readyState==4 && http_request.status==200){ if (http_request.responseText=="OK"){ Update(); } else { document.getElementById('Response').innerHTML=http_request.responseText; } } }
  http_request.open('POST', 'add.php?username='+username+'&cache='+cache, true);
  http_request.send(null);
}

function Delete(username) {
  http_request = false;
  if (window.XMLHttpRequest) { // Mozilla, Safari,...
      http_request = new XMLHttpRequest();
      if (http_request.overrideMimeType) {
        http_request.overrideMimeType('text/html');
      }
  } else if (window.ActiveXObject) { // IE
      try {
        http_request = new ActiveXObject("Msxml2.XMLHTTP");
      } catch (e) {
        try {
            http_request = new ActiveXObject("Microsoft.XMLHTTP");
        } catch (e) {}
      }
  }
  if (!http_request) {
      return false;
  }
  http_request.onreadystatechange=function(){ if (http_request.readyState==4 && http_request.status==200){ Update(); } }
  http_request.open('POST', 'delete.php?username='+username, true);
  http_request.send(null);
}

function Update() {
  http_request = false;
  if (window.XMLHttpRequest) { // Mozilla, Safari,...
      http_request = new XMLHttpRequest();
      if (http_request.overrideMimeType) {
        http_request.overrideMimeType('text/html');
      }
  } else if (window.ActiveXObject) { // IE
      try {
        http_request = new ActiveXObject("Msxml2.XMLHTTP");
      } catch (e) {
        try {
            http_request = new ActiveXObject("Microsoft.XMLHTTP");
        } catch (e) {}
      }
  }
  if (!http_request) {
      return false;
  }
  http_request.onreadystatechange=function(){ if (http_request.readyState==4 && http_request.status==200){ document.getElementById("list").innerHTML=http_request.responseText; } }
  http_request.open('GET', 'list.php', true);
  http_request.send(null);
}

</script>
Please help and thank you