Awilum/monstra-cms — pull request #156 by bernte (2013-11-17 16:50:16+00:00)
Title: Update index.php

503 is the correct server response for "We're closed". If you substitute a normal HTML page saying "We're closed" and serve a 200 it's very likely to get indexed by Google.

If you give the Googlebot a 503, it will just go away and come back later without indexing what you give it.