Unlike the previous WYSIWYG editor, the new editor has different usage conditions regarding HTML code. In the previous editor, each vertical block was separated with tags. Now every block is like a table and begins and ends with table tags.
This is why templates made for the new Drag and Drop editor will also be usable in the previous editor. While templates made in WYSIWYG editor will not work properly in the new editor and will be identified as faulty.
Avoid using HTML attributes like cellspacing and cellpadding: you can impose indentations between blocks within the editor or you can use the style attribute value padding.