Numbered Headings in Markdown via CSS

styles.css

h1 {
  counter-reset: h2counter;
}
h2 {
  counter-reset: h3counter;
}
h3 {
  counter-reset: h4counter;
}
h4 {
  counter-reset: h5counter;
}
h5 {
  counter-reset: h6counter;
}
h6 {
}

h2:before {
  counter-increment: h2counter;
  content: counter(h2counter) ".\0000a0\0000a0";
  border-left: 5px solid black;
  padding-left: 5px;
}

h3:before {
  counter-increment: h3counter;
  content: counter(h2counter) "." counter(h3counter) ".\0000a0\0000a0";
  border-left: 4px solid black;
  padding-left: 4px;
}

h4:before {
  counter-increment: h4counter;
  content: counter(h2counter) "." counter(h3counter) "." counter(h4counter)
    ".\0000a0\0000a0";
  border-left: 3px solid black;
  padding-left: 3px;
}

h5:before {
  counter-increment: h5counter;
  content: counter(h2counter) "." counter(h3counter) "." counter(h4counter) "."
    counter(h5counter) ".\0000a0\0000a0";
  border-left: 3px solid black;
  padding-left: 3px;
}

h6:before {
  counter-increment: h6counter;
  content: counter(h2counter) "." counter(h3counter) "." counter(h4counter) "."
    counter(h5counter) "." counter(h6counter) ".\0000a0\0000a0";
  border-left: 3px solid black;
  padding-left: 3px;
}