title: How to know whether WebBrowser navigating a error page?
body: <p>for example, we navigating to <a href="http://www.ggg111.com" rel="noreferrer">http://www.ggg111.com</a>, it's a error URL. but in WebBrowser it display a error page with this:</p>
  
  <pre>
  The webpage cannot be found 
   HTTP 400  
     Most likely causes:
  There might be a typing error in the address. 
  If you clicked on a link, it may be out of date. 
  
     What you can try: 
       Retype the address.  
  
       Go back to the previous page. 
       Go to  and look for the information you want.  
  </pre>
  
  <p>how to know whether WebBrowser navigating a error page?</p>
  
  <p>also check this:
  <a href="https://sso.youshang.com/sso/userAuthnAction.do1" rel="noreferrer">https://sso.youshang.com/sso/userAuthnAction.do1</a></p>
  
  <pre>
  HTTP Status 404 - /sso/userAuthnAction.do1
  type Status report
  message /sso/userAuthnAction.do1
  description The requested resource (/sso/userAuthnAction.do1) is not available.
  </pre>