(Note on 7/26/03: Below you will find a bad reference to Apendix A of the HTML 4.0 specification. This is incorrect. The reference is actually in Appendix A of the CSS 2.0 specification.)
A lot of artists fear a blank canvas. It's a almost sterotype that writers get blocked when faced with a blank page. I'm a little this way about style sheets. I use pretty plain HTML typically without class or id attributes if possible. How many different classes of h1 can we reasonably expect users to be able to apply?
I remembered that when I was learnings CSS I had found "the default" style sheet. At the end of the HTML4.0 specification, there is a typical style sheet, based on "extensive research into current UA practice." Which means that all the default CSS selectors are specified here in such a way that if we don't override the values with our own style declarations, this is what is rendered. (Sort of.)
See the sample and a more complete explanation of the file in Appendix A.