H1-H6 font sizes in HTML

Question

In HTML (and in typography in general, I suppose), there appears to be some defined sizes for H1-H6 -elements.

Ie., if the baseline font size is 16px (or 100%), then h1

Answer 1

I think it is up to the browser, which may even even let the user define the font sizes (I remember opera doing that). The HTML spec doesn't go into much detail:

There are six levels of headings in HTML with H1 as the most important and H6 as the least. Visual browsers usually render more important headings in larger fonts than less important ones.

This is intentional since HTML is designed to describe the structure, not the presentation of the document.