do you have use this line
<script type="text/javascript" src="Script/jquery-1.4.1.js">
</script>
and then use
<script type="text/javascript">
$(function () {
$("#Button6").click(function (evt) {
evt.preventDefault();
$('#Panel1').slideToggle('slow');
});
});
</script>
See these links
slidetoggle of Jquery.
see example
accordion-with-jquery