During the past days of ASP.NET 1.1 we used to use multi panels whenever we needed to separate our controls in a specific block and to show/hide the panel whenever needed
now ASP.NET 2.0 provide us with the Multiview control it is used for the same concept with less overhead

here is an example

<asp:MultiView ID="MultiView1" runat="server" ActiveViewIndex="0">
<asp:View ID="view1" runat="server" >
</asp:View>
<asp:View ID="view2" runat="server"></asp:View>
</asp:MultiView>

and then you can use the following to activate a specific view

MultiView1.SetActiveView(view2);