title: Canonical for page returning error
body: <p>If for some reason on my website an error occurs, the page will return response 500 and as content it will show some information for the vistor about what happened and where he can continue.</p>
  
  <p>For example:</p>
  
  <p>/product/somebook -> Normal HTTP 200 OK with content about this book</p>
  
  <p>When internal error happens:</p>
  
  <p>/product/somebook -> Error HTTP 500 returns page with information about what to do now (no redirect)</p>
  
  <p>If the reponse is 500 should the page contain a canonical tag to for example /error ?</p>