Show Section On Button Click

Multiviews

Multiviews allow for easily switching between sections of content:

<asp:MultiView runat="server">
    <asp:View runat="server">
        First Content
    </asp:View>
    <asp:View runat="server">
        Second Content
    </asp:View>
</asp:MultiView>

Panels

Panels are good for when each section isn't mutually exclusive:

<asp:Panel runat="server">
    Main Content
</asp:Panel>
<asp:Panel runat="server">
    Extra Content
</asp:Panel>

Controls

You can also show/hide pretty much any ASP.NET or HTML control so long as it has a runat="server" on it. Just set its Visible property to true or false.

<div id="myDiv" runat="server">
    Extra Content
</div>

myDiv.Visible = false;