ajax.php

<?php
  require_once("grid.php");
  $grid = new Grid("users", array(
    "save"=>true,
    "delete"=>true
  ));
?>

HTML Setup.html

<table class="users" action="ajax.php">
  <tr>
    <th col="Username">Username</th>
    <th col="FirstName">First Name</th>
    <th col="Lastname">Last Name</th>
    <th col="Email">Email</th>
  </tr>
</table>

script.js

<script>
  $(function() {
    $(".users").grid();
  });
</script>

For me it only works, if I add the class="users" to the table