The mysterious get_aspx_ver.aspx page in Visual Studio 2003
Weird... we are not executing any code when loading the project... wrong, this mysterious page is called...
Visual Studio .NET 2003 makes an http request to the non existent web page: http://yourserver/yourweb/get_aspx_ver.aspx in order to determine the ASP.NET version installed on your web server (this information is returned in the http headers for the request). Since the page does not exist on your web server, your error handler is called.
One possible work around is to have your error handler ignore failures to this page, which is exactly what we did.
Related problems are described here:
http://support.microsoft.com/default.aspx?scid=kb;en-us;825792
and on this post in aspnetresources.com.
TTYL!