ASP.NET Error: Server Error in Application "Resource not found"

After transferring some files via Visual Studio to a website, a stared getting the HTTP 404 error above. The file I was searching for, test.aspx, was definitely there as were other .htm and .asp files around it. After searching through a myriad of posts, checking if ASP.2.0 was hooked up properly, that my directories were correct, that the application was there, that the DNS was indeed correct, I found the stupid problem: an app_offline.htm file had been generated during the update, and had not been removed. Apparently in Windows 2003 /IIS6/ .NET 2, this will result in an HTTP 404 error that gives no clue as to it’s cause. I hope this saves you some time.

Thanks,
Marco