This tutorial is based on on the W3C recommendation, where the idea is to
use CSS wherever possible, but to still include semantic HTML to support older browsers. HTML
is a markup language, and is by far the most commonly used language
on the Web. Markup languages give structure to a document. They say what parts are headings, what parts are paragraphs,
what parts are bullet lists, etc.
The W3C HTML 4.0.1 specification