To turn your website online or offline simply log in to your Dashboard and toggle your site from Offline to Online or vice versa:
Why turn your website offline?
If you want to stop people from viewing your website you can set it offline. This is commonly done when the website is under construction and not ready to be released for the world to see. You can still access your website by logging in to your Dashboard and going to Editor or Preview.
Please note that setting your website offline will also stop search engines like Google and Bing from being able to index your website. If left offline for a long period of time this could result in your website being removed from their search results, and it can take some time to gain your position back again.