<form id="form1" runat="server">
 <asp:ScriptManager ID="asm" runat="server" />
 <div>
 <ajaxToolkit:Accordion ID="acc1" runat="server" 
 HeaderCssClass="header" ContentCssClass="content" 
 Width="300px" FadeTransitions="true">
 </ajaxToolkit:Accordion>
 </div>
</form>