Greetings
This might be helpful to some of you until "off-line for maintenance" feature is added.
1. Changing permissions public_html folder - worked great.
2. If you'd like to send visitors to a page explaining why your site is down, instead of just denying them access without an explanation, you can make a .htaccess file that catches all requests and directs them to one page, like so:
RewriteEngine on
rewriterule ^(.*)$
http://example.com/maintenance.html [r=301,nc]
If you save that as a file called .htaccess to public_html it will redirect all visitors to
http://example.com/maintenance.html, obviously you'd fill in your own address, and you will of course have to set the permissions for public_html back to 755.