if iframe exist in ie8 ,jquery animate with time can't work.

if iframe exist in ie8 ,jquery animate with time can't work.

when click in ie8,it can't work.
if remove iframe,it can work.
why?



<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<head>

<style>
body{margin:0;  padding:0;}
#hiddenbar{display:none;width:250px;height:500px;border:1px solid;position:absolute;right:0;top:0;    }
#editing{width:300px ;height:300px ;border:1px solid;}
</style>

<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
 //  document.getElementById("editing").contentWindow.document.designMode='On';

$(document).click(function(e){$("#hiddenbar").show(1000)})
$("#hiddenbar").mouseleave(function(){$(this).hide(500)})
})
</script>
 </head>

 <body>
<iframe name="editing" id="editing"></iframe>
<div id="hiddenbar"> </div>
 </body>
</html>