title: Proper use of HTTP Error Codes. 550 - Why is it 5xx instead of 4xx?
body: <p>Today a co-worked used a 550 error on a delete action when the user doesn't have permission which at first looked to me bad because as I'm aware of, that kinda error looks like a client (aka 4xx) error to me and not a server (aka 5xx). </p>
  
  <p>When looking at the description, it suggest exactly that it was used correctly. Instead of a 401 error, which I was using with some 'problems' before.</p>
  
  <p>Problem of 401 error is : If user A is logged in, and try to do an action that returns a 401 it can suggest that you must 'login' since you don't have valid credentials to access that http resource. Problem with this approach is that if user is logged, server knows that he doesn't have the permission, in this case, looks like a 550 it's more appropriate but doesn't look quite to me that a 550 error should be used in this scenario.</p>
  
  <p>Question is:
  What's the proper use (if any) of 550 error, in web based applications. I understand it's use in FTP and SMTP relay usage.
  If some logged in user, sends a request of an action which is not permitted, which error should be returned ?</p>
  
  <p>Thanks!</p>