By default WordPress saves a history of all the changes you make to a page. They are stored as past page revisions. You can browse and restore these revisions. If something happens on your page, you accidentally delete or break something, the revision history will allow you to go back to a previous version. Access the revision history by clicking the link in the “Publish” menu to the right of the Page/Post Editor. You can see a summary of past revisions below the main Page/Post Editor.