Clicking on 'Preview' will open a new tab that displays the page you are currently working on.
Note: 'Preview' will not display the Home Page or your Contact Us page correctly. This is because these pages are dynamically created by us. The best way to view these pages (and all other pages if you like) is to open a new tab and view them on your site. Then come back to your BackOffice make your changes, click on your site tab and refresh the browser to see your changes.