Remember too keep the QUICK ACCESS, LANGUAGE and LOCATION BAR closed, before you preview/publish.
You can click on the bars to edit the content inside the expandable menus, and when you are done you can click again on the bars to close them.
Close the menu bars before preview/publish. That way you can make sure that they will not block the content on other pages.
To close, select the menu and uncheck the option that says: "Show lightbox parts while editing" .
To edit the menu bars again, you can check the same option and the submenus will show up.