<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Reference</title>
<style>
.clamp {
  display: -webkit-box;
  -webkit-box-orient: vertical;
  font: 16px / 32px monospace;
  white-space: pre;
  background-color: yellow;
}
</style>
<div class="clamp"><div>Line 1
Line 2<fieldset>Line 3
Line 4<legend>Line 5
Line 6</legend></fieldset>Line 7…</div></div>
<p>Following content.</p>