To make some site that is publicly available on,, for ex: address:
only visible to admin roles or developers while working on site online, open your index.php in your active theme and somewhere on the top of that file add next line:
<?php if( ! is_user_logged_in() ) exit ; // rest of the theme calls.. get_header(); // ...
after that, only logged in user will see developement site, and all others, including web crawlers will see beautiful white canvas :)