title: Does nginx, as I suspect, put "Welcome to Nginx!" when it doesn't know what else to do?
body: <p>I'm debugging a simple (Docker) proxy server which, so far as I know, doesn't have a "default web site" or anything like that.  I think it's getting <code>302</code> responses from upstream but I do not yet know why.  But what <em>is</em> interesting is that I'm getting <em>"Welcome to Nginx!"</em>  Even though I don't think there is a web-site file that would actually produce it nor any reason to go to such a place.</p>
  
  <p>So ... does nginx sometimes produce that response "on its own?"  If so, it would greatly help my troubleshooting if someone could tell me, "under what circumstances?"  If this is a <em>clue,</em> I'd like to understand that clue ...</p>