When using the built-in webserver in debug mode, the static files are
handled automatically. From the Django docs:
During development, if you use django.contrib.staticfiles, this will
be done automatically by runserver when DEBUG is set to True (see
django.contrib.staticfiles.views.serve()).
This method is grossly inefficient and probably insecure, so it is
unsuitable for production.
This means, when using a real webserver, it also has to serve the static
files, i.e. CSS and JavaScript. For that, one needs to run `./manage.py
collectstatic` first.
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