User controls are a very powerful part of ASP.Net.
in classic ASP, many people used include files for template functions... user controls can be used to extend this concept
These are some very simple examples of how you can use user controls to handle some of the layout... just use the same templating concepts discussed in this article
Header.ascx
<script language="VB" runat="Server">
public title as string
sub page_load(o as object, e as eventargs)
lblTitle.text = title
end sub
</script>
<html>
<head>
<title><asp:label id="lblTitle" runat="server" / ></title>
</head>
<body>
Footer.ascx
<script language="VB" runat="Server">
public copyright as string
sub page_load(o as object, e as eventargs)
lblCopy.text = copyright
end sub
</script>
<hr>
<asp:label id="lblTitle" runat="server" / >
</body>