If you coded 100% of the content using the WYSIWYG Editor, then it should display accurately in the WYSIWYG, however, if you have custom content that was coded by scratch (HTML), then it may not recognize some of the tags that are being used. It's important to note that the WYSIWYG Editor is simply a rough interpretation of the HTML code on the back end. The preview page may also display differently after Luminate has rendered the content from the PageWrapper/Stationery, or other components such as a reusable PageBuilder page.