CSS for adding header numbering to google documents

GoogleDocsHeadingNumbers.css

/**
 * CSS to add section numbers to top-level headings in 
 * a Google Docs (or any HTML) document.
 * 
 * See <http://www.w3.org/TR/CSS2/generate.html> for 
 * more details. 
 */
body {
  counter-reset: section;
}
h1:before {
  counter-reset: subsection;
  counter-increment: section;
  content: counter(section) ". ";
}
h2:before {
  counter-reset: subsubsection;
  counter-increment: subsection;
  content: counter(section) "." counter(subsection) ".  ";
}
h3:before {
  counter-increment: subsubsection;
  content: counter(section) "." counter(subsection) "." counter(subsubsection) ". ";
}