I would argue that developers should aim for 0 error messages ever. If your software requires an action to be performed before moving on, then redirect them to

I would argue that developers should aim for 0 error messages ever. If your software requires an action to be performed before moving on, then redirect them to the action, highlight the point of interest, and give a little alert at the top that tells them what to do. When you have a scary error message, users get scared.