The WYSIWYG presents HTML through style sheets which is the web standard. This is why the <font> tags are replaced with the <span> tags. If you plan to write your own HTML, then we recommend using plain text for 100% of your content. If you attempt to modify custom HTML with the WYSIWYG editor, it may have undesirable consequences, such as translating your HTML tags in to style sheets which is it what the WYSIWYG understands.