css - CSS でカウンターが増加しない

Question

この例では:

h3 {
  font-size: .9em;
  counter-reset: section;
}
h4 {
  font-size: .7em;
  counter-reset: subsection;
}
h3:before {
  counter-increment: section;
  content: counter(section)" ";
}
h4:before {
  counter-increment: subsection 2;
  content: counter(section)"." counter(subsection)" ";
}

<h3>Favorite Movies</h3>
<h4>District 9</h4>
<h4>The Matrix</h4>
<h4>The Cabin in the Woods</h4>

<h3>Others</h3>
<h4>Minority Report</h4>
<h4>Lord of the Rings</h4>
<h4>Fargo</h4>

私はそれを見てsection、subsection増加しません。

このコードの問題は何ですか?