Please refer this code.
HTML
<form id="form1" runat="server">
<div>
<cc1:ToolkitScriptManager runat="server">
</cc1:ToolkitScriptManager>
</div>
<cc1:Accordion ID="Accordion1" runat="server">
<Panes>
<cc1:AccordionPane ID="apRegistrationForm" runat="server">
<Header>
<a href="#">Registration Form</a>
</Header>
<Content>
<table>
<tr>
<td>
UserName
</td>
<td>
<asp:TextBox ID="txtRegisterUserName" runat="server" />
</td>
</tr>
<tr>
<td>
Password
</td>
<td>
<asp:TextBox ID="txtRegisterPassword" runat="server" />
</td>
</tr>
<tr>
<td>
Confirm Password
</td>
<td>
<asp:TextBox ID="txtConfirmPassword" runat="server" />
</td>
</tr>
</table>
</Content>
</cc1:AccordionPane>
<cc1:AccordionPane ID="apLogin" runat="server" Width="300" HeaderCssClass="header"
HeaderSelectedCssClass="header_selected" ContentCssClass="content">
<Header>
<a href="#">Login</a>
</Header>
<Content>
<table border="0" cellpadding="0" cellspacing="0">
<tr>
<td>
UserName
</td>
<td>
<asp:TextBox ID="txtUserName" runat="server" />
</td>
</tr>
<tr>
<td>
Password
</td>
<td>
<asp:TextBox ID="txtPassword" TextMode="Password" runat="server" />
</td>
</tr>
<tr>
<td colspan="2">
<asp:Button Text="Login" runat="server" />
</td>
</tr>
</table>
</Content>
</cc1:AccordionPane>
</Panes>
</cc1:Accordion>
</form>
Screenshot