title: Best way to center a <div> on a page vertically and horizontally?
body: <p>Best way to center a <code>&lt;div&gt;</code> element on a page both vertically and horizontally?</p>
  
  <p>I know that <code>margin-left: auto; margin-right: auto;</code> will center on the horizontal, but what is the best way to do it vertically, too?</p>