HTML by itself doesn't give you much other than structure in a page and there's no guarantee that every browser out there will render the tags in the same way. So along came style sheets. Style sheets enhance HTML as a word processor enhances plain text.
But... no guarantees what a browser might do with a style sheet, any more than what a stylist might do to your hair, but we can hope for the best.
This is not a designer's dream style, but it illustrates the power.