jQuery: Using the jQuery $.post() function

Got this from the server:
The jQuery Code START
    
    <script type="text/javascript" src="./jquery-1.5.1.js"></script>
    <script src="http://code.jquery.com/jquery-latest.js"></script>
  
    <script type="text/javascript">
      $(document).ready(function() {
        $.post("poster.php", {data: 1},
          function(data) {
            $("div").text(data);
          }); 
     });
    </script>
    
    <style type="text/CSS">
        <!--
        .code { color: red; }
        .back { background-color: yellow; }
        -->
   </style>
  </head>

  <body>
    <h1>jQuery: Using the jQuery $.post() function</h1>
    Got this from the server: <div></div>
    
    <-- Contents of poster.php -->
    <?php
    if ($_POST["data"] == "1") {
        echo 'You sent the server a value of 1';
    }
    if ($_POST["data"] == "2") {
        echo 'You sent the server a value of 2';
    }
    ?>