Simple animate jquery not working in IE

1

Hi,
I have a simple animate function on a div container. Works great in FF. Doesn’t work at all in any IE. I want to know if it’s the js or css. I have read a few things but nothing definite on why it doesn’t work.
Here is the (http://www.headfirstgraphics.com/work/solvency2explained/animatedpanels.html),

<script type="text/javascript">
$(document).ready(function(){
    
  $("#panel")
    .animate({marginTop: "=300px", height: "+=100px"})
    .delay(1000)
    .animate({marginTop: "-=300px", height: "+=100px"})
    .fadeIn();
  });

</script>

<style type="text/css">
body {
    margin: 0 auto;
    padding: 0;
    font: 75%/120% Arial, Helvetica, sans-serif;
}
#panel {
    background: #000000;
    height: 200px;
    width:960px;
    display:none;
}
</style>
</head>

<body>

<div id="panel">
    <!-- you can put content here -->
</div>

Any ideas why IE isn’t liking this?

Thanks
Will