title: margin-left: auto and margin-right: auto not working on input
body: <p>I have an input in a form that I am trying to align in the center. Usually <code>margin-left:auto</code> and <code>margin-right: auto</code> fail to respond when <code>display: block</code> isn't added to the CSS. I have added <code>display: block</code> to my CSS but still it isn't display as I would like it to.</p>
  
  <p>I've made a JSFiddle to keep easier to understand: <a href="http://jsfiddle.net/XnKDQ/97/" rel="noreferrer">http://jsfiddle.net/XnKDQ/97/</a></p>