title: Are rems replacing ems in CSS?
body: <p>I was reading about <a href="http://www.w3.org/TR/css3-values/#rem-unit"><code>rem</code> units in CSS3</a>, and was a little confused. If you use <code>rem</code>, do you still use <code>em</code> or does that replace it?</p>
  
  <p>For example:</p>
  
  <pre><code>.selector {
      margin-bottom:24px;
      margin-bottom:2.4rem;
      font-size:16px;
      font-size:1.6rem;
  }
  </code></pre>
  
  <p>or</p>
  
  <pre><code>.selector {
      margin-bottom:24px;
      margin-bottom:2.4em;
      margin-bottom:2.4rem;
  }
  </code></pre>
  
  <p>Just trying to figure out if <code>rem</code> takes the place of <code>em</code>, or if it's just another unit.</p>