...
Click the orange “Done” button 
to validate the page once you have saved the page and are ready to test it. This button reports on any missing elements , and reminds you about other things you may want to think about.
You can then view the page as if it were live by clicking the magnifying glass (Preview button). The page is shown in a new tab in “DEMO” mode (which you can confirm by viewing the URL – it will end with “?mode=DEMO”). You can submit the form and send out e-cards to yourself. In this way, you can confirm that the action is working exactly how you want it to.
...