OK, I think the whole world knows this, or at least has already blogged about it, but I’m going to add it here so that future-me can look it up next time I need it.

When doing maintenance on your asp.net 2.0 web site, if you put a file named “app_offline.htm” in the root of the site, the ASP.Net runtime will serve that file rather than processing the site.  In this way you can update and maintain the rest of the site, and your visitors will see the app_offline.htm file until it is deleted.

(Future-me, did past-me get an app_offline.htm updated with our company name, product name, and contact info?  Even though the site is off-line, I still want visitors to know about our products!)