WebsiteBuilder: Save History
WebsiteBuilder keeps a history of each save point on your site. You can view and revert to any of these save points at any time. So if you make some changes that you decide not to use, you can easily switch back to the previous version, or even several versions back. To restore a save point, click on the Manage link on the left or the indicated icon near the top right.
You will see the save points on the left, listed from most recent to oldest. You can see if that version was published or not and you can add notes if desired. Click on the save point and it will preview the site as it was at that save. Anytime you find the save point you desire, click "open in editor" and then you can save and publish.