Say an ASP.NET website suddenly starts returning a 500 error code with a blank page (not serving the configured error document). Where might I find error reports and/or clues as to what is happening, besides:

  • Email error notifications
  • Event Viewer (Application log)
  • Task Manager (memory usage, CPU usage)
  • Windows HTTP logs (C:\Windows\System32\LogFiles\httperr)
  • ASP.NET log files (C:\inetpub\LogFiles)

Also, what are common first steps? For example, does restarting the web site in IIS often resolve issues?


If you don't get an ASP.NET error page ("Yellow Screen of Death"), then that typically suggests that IIS encountered an error before it managed to fire up the ASP.NET engine. IIS will usually show a more elaborate error page if you access the site from a browser running on the server running the site (i.e. from a non-remote client).

Often, this is a problem with the application configuration in Web.config that prevents IIS from starting ASP.NET.

The sources you list are also good, with Event Viewer probably being the best one.

  • Yep, the event viewer is the best place to start, it will normally capture all of the errors that IIS encounters with anything related to starting the app. After that I would take a look at ELMAH, its a good tool and easy to add to your app for more detailed error logging options. – Brent Pabst Jul 30 '12 at 18:17

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