Unpublishing a page allows you to work on a page as a draft before publishing it. This means that the page still exists but is not visible or accessible to your visitors. When you are logged in as Admin you can always view and edit your unpublished pages. Make sure that you do not unpublish a start page, otherwise people will not be able to see your site. If the page you wish to unpublish is a start page, choose a new start page first.
To publish or unpublish a page:
Click on "Manage Pages" in the top-left corner
Select option "Edit existing pages"
Hover over your page and click "Settings"
Scroll down and press the "Un-publish the Page" button.
After that, the "Un-publish the Page" button will be replaced with the "Publish" button, that can be used later to bring the page back to your website.