What's the best practice approach and/or easiest to put up a temporary page at http://www.mysite.com/ announcing the site will be offline?

I certainly don't want people to access any of the pages directly (bookmarks for example).

Comments

Create a new page, add whatever text you'd like to say the site is down. Go to admin/config/system/site-information and set the "Default front page" to the new page (it'll be "node/2" or something like that). If you edit the new page you'll be able to see the node ID in the URL. Then you can alter block settings to omit them from that page as well (menu's, images, ads, etc).

You can put your Drupal installation into maintenance mode, which will restrict access to your website. It will also display a message of your choice to notify your customers.

Enable that by logging in as administrator > Configuration. You will notice the Maintenance Mode option under the Development tab.

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