title: Why does margin: auto only work horizontally and not vertically?
body: <p>I have seen that while developing websites, vertically centering a container (of fixed height) inside a container of random height always comes as a nightmare for the web developer (at least, me) while when it comes to horizontal centering a container (of fixed width) inside a container of random width, the <code>margin:0px auto;</code> tends to serve an easy way out in the standard model.</p>
  <p>When things can be as simple as that why doesn't CSS work out with the <code>margin:auto 0px;</code> when it comes to centering a container of fixed height inside a container of random height? Is there any specific reason to do so?</p>