Mif2Go normally provides a header that indicates compliance with W3C's HTML 4 specification. The default header includes a "transitional" qualifier that permits use of some formatting code that in HTML 4 is deprecated in favor of CSS. Unfortunately, browsers have not quite managed yet to implement CSS well enough so that you can depend on CSS alone; not even CSS1, let alone CSS2. So "strict" compliance has to wait.
> 12 Converting to HTML > 12.3 Supplying values for the <head> element