title: WPF WebBrowser events for HTTP errors?
body: <p>I have a WPF application and I'm using the WebBrowser control to display some content from a public website. </p>
  
  <p>Sometimes in weird edge cases when the network connectivity is flakey, the web browser will show the "This program cannot display the webpage" error page. Is there some way to listen to the WebBrowser to detect when this occurs, so I can load a placeholder?</p>