Hiding an entire site?

Is it possible to hide an entire Omeka site while developing the archive? I know that you can make an exhibit "non-public" while designing the exhibit, but what about the whole site?

There's not a site-wide switch, but Items and Collections can be non-public, too.

If you don't mark anything as 'Public' then visitors to the site will just see an empty shell (though you will be able to see all your items, exhibits, etc while logged in).

If you don't want anyone to see even that, you can do a header redirect, and send visitors to some other page (like some kind of static "coming soon" page). That might look something like:

$user = Omeka_Context::getInstance()->getCurrentUser();
$authenticated =('super'||'admin'||'contributor'||'researcher');
$redirect = 'http://google.com';
if($user->role != $authenticated):

The above would redirect the user to Google, based on the $redirect variable. Users who are logged in will still be able to see the site.

You need to put this at the very top of your index page (as well as any other pages you want hidden). I'm not sure, but you might be able to just put it at the very top of header.php but I think it needs to be the first thing loaded by the browser to work correctly.