To make your Grav website unavailable to visitors, replacing it with a simple message, do this:

1. Log in to the Grav Admin dashboard.
2. Click on the Gantry 5 button in the admin sidebar on the left.
3. Click in the top right corner on the Extras button and select Platform Settings.
4. Find where it says Offline and select the Yes switch.
5. You can then change the Offline Message in the field below to give your visitors some explanation about why your website is unavailable.
6. Click the Save button on the top right to implement the new settings.
7. You should see a message confirming the settings have been changed.