This is a pretty handy feature for taking your ASP.NET 2.0 app offline (for maintenance or whatever) and displaying a friendly message explaining why the site is down.

Just place a file called 'App_offline.htm' in the root of your site with whatever message you want to give your users and bingo your app shuts down and the contents of App_offline.htm are served. Just delete or rename App_offline.htm to something else to bring the app back online again.