This example uses the Outlook theme defined in the root App_Themes folder.
Source Code & Description
Themes and Skins - The Themes and Skins feature of ASP.NET 2.0 allows you to factor style and layout information into a separate group of files, collectively called a Theme. A Theme can then be applied to any site to affect the look and feel of pages and controls within the site. Style changes to a site can then be easily maintained by making changes to the Theme, without having to edit the individual pages in your site. Themes can also be shared with other developers.
<%@ Page Theme="Outlook" AutoEventWireup="false" ... >