Suddenly for no apparent reason, one of our applications (after publishing) started giving this 404 error message:

Server Error in ‘/xxx’ Application.
—————————————————-
The resource cannot be found.
Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly.
Requested Url: /xx/xx.aspx

This error was coming on all pages in the application, I checked and re-checked ASP.NET version in IIS, read-write permissions on the published folder, application pool setting, trailing slash problem (http://support.microsoft.com/kb/894670/en) and every other thing, but none helped!

I did some googling but came up with same results, these are the links I checked:

http://cephas.net/blog/2005/07/14/aspnet-the-resource-cannot-be-found/

http://forums.asp.net/t/1186539.aspx

By chance I noticed this link: http://dotnet.org.za/armand/archive/2005/07/03/38757.aspx about removing app_oflline.htm file from the root directory.

And I realized that we too have the app_offline.htm file and the moment we removed it, the application worked like a charm!

Hope this helps others!