title: What happens if we don't use <!DOCTYPE html> statement ? (on modern and old browsers)
body: <p>I'm a crack person as you see on my profile picture. If we don't use HTML5 DOCTYPE statement, all modern browsers goes heuristic or inherit mode?</p>
  <p>Modern browsers seem our page as HTML5 and old ones suddenly get mad about</p>
  <pre><code>&lt;!DOCTYPE HTML PUBLIC &quot;-//W3C//DTD HTML 4.01//EN&quot; &quot;http://www.w3.org/TR/html4/strict.dtd&quot;&gt;
  </code></pre>
  <p>What happens?</p>