need code help pls!

need code help pls!

i am building a really basic page to get my head around .position
i have 2 divs on the page and all i want to do is play around with their positioning.
below is my page code so far.
it doesn't work and i don't know why.
all help appreciated. thanks
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  
        <script type="text/javascript" src="js/jquery-1.4.2.min.js"></script>
        <script type="text/javascript" src="js/jquery-ui-1.8.1.custom.min.js"></script>
       
<script type="text/javascript">
$(function() {
     // test position
     $("#move-me").position({
    "my": "right top",
    "at": "right top",
    "of": $("#thing")
});
</script>

<style type="text/css">
#move-me {background-color:#00FF00; width:300px; height:100px;}
#thing {background-color:#CCCCCC; width:500px; height:600px;}
</style>


<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Test Position</title>
</head>
       
<body>
<div id="thing">#thing</div>
   
<div id="move-me">#move-me</div>

</body>
</html>