Reasoning Behind ASP.NET Framework
In a nutshell, ASP.NET is a web application framework that undergoes compilation at runtime. This means that your page transitions from objects and controls to HTML, CSS, and JavaScript; the encrypted JavaScript (ScriptResource.axd) inaccessible within your HTML page. Helpful Link on ScriptResource.axd
Solution to the Problem
The good news is, if you are utilizing AJAXToolKit (which is quite an assumption), you have the option to utilize jQuery UI Accordion with just one section. Both options have been tested and yield similar outcomes. I trust this information proves useful! jQuery Accordion Reference
Example of ASPX Implementation using AJAX (Collapsible Panel):
<form id="form1" runat="server">
<div>
<asp:ScriptManager ID="ScriptManager1" runat="server" />
<ajaxToolkit:CollapsiblePanelExtender runat="server"
TargetControlID="Panel1"
Collapsed="true"
ExpandControlID="LinkButton1"
CollapseControlID="LinkButton1" />
<asp:LinkButton ID="LinkButton1" runat="server">Panel</asp:LinkButton>
<asp:Panel ID="Panel1" runat="server">
This is a Test
</asp:Panel>
</div>
</form>
Example of HTM Utilizing jQuery (Accordion):
<head>
<title></title>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.8.21/jquery-ui.min.js"></script>
<script type="text/javascript">
$(document).ready(function () {
$('#Panel1').hide();
$('#pnlLink').click(function () {
$(this).next().toggle();
return false;
}).next().hide();
});
</script>
</head>
<body>
<a id="pnlLink" href="#">Panel</a>
<div id="Panel1">
<div>
This is a test</div>
</div>
</body>