title: Fix "invalid host header" in Angular
body: <p>I have an app in Angular v4 which have to change the scss dependong of the url of access.
  For example:
  if link in the browser is "example.com" then the app have background-color: black
  if the link is"example2.com" then the background-color: red</p>
  
  <p>I have the next problem:</p>
  
  <p>when I go to the hosts in C:\Windows\System32\drivers\etc and I set the next configuration in hosts
  127.0.0.1   example.com
  127.0.0.1   example2.com</p>
  
  <p>then I run the app with "example.com:4200" the app doesn't run... the browser show me this message</p>
  
  <p>"invalid host header"</p>
  
  <p>How do I fix this problem?</p>