center iframe

best way and more simple to center an iframe on your webpage is :
<p align="center"><iframe src="http://www.google.com/" width=500 height="500"></iframe></p>

<div class="iframe-container">
  <iframe src="https://jsfiddle.net/8z9s1t6x/2/"></iframe>
</div>

<style>
  .iframe-container {
		text-align:center;
  		width:100%;
  }
</style>