Step 1
Go to "Configuration" then "Maintenance mode".
Step 2
1) Make sure the "Put site into maintenance mode" box is checked
2) Enter the message you want visitors to see during the interruption.
3) Click "Save configuration".
Step 4
You'll now see a message saying "The configuration options have been saved".
Step 3
You will be able to browse around your site without problems but visitors who aren't logged in will see the message above.
If you log yourself and can't get back in, just add /?q=user after your site address and you'll be back to the user login page.
