We use the following control on aspx page

Check this Article - http://http://www.mindstick.com/Articles/9f7f0045-fb3e-4257-8f89-9ca2a5d48255/ 

<div>

 <%--Using ScriptManager or ToolkitScriptManager according toolkit version--%>
         <asp:ScriptManager ID="ScriptManager1" runat="server">
         </asp:ScriptManager>
 <%-- add the RoundedCornersExtender, panel and login control--%>
         <cc1:RoundedCornersExtender ID="RoundedCornersExtender1" runat="server" TargetControlID="Panel1">
         </cc1:RoundedCornersExtender>
         <asp:Panel ID="Panel1" runat="server" Width="250px" HorizontalAlign="Center" BackColor="Orange">
         <asp:Login ID="Login1" runat="server">
         </asp:Login>
         </asp:Panel>
            </div>