title: how to specify image size in pixels
body: <p>Quick question about specifying the size of images in pixels:</p>
  
  <pre><code>&lt;img src="/logo.jpg" alt="logo" width="200px" height="120px" /&gt;
  </code></pre>
  
  <p>or</p>
  
  <pre><code>&lt;img src="/logo.jpg" alt="logo" width="200" height="120" /&gt;
  </code></pre>
  
  <p>I've been always putting in the px but recently noticed that very few people do this. Am I better off leaving that out? Does it matter one way or the other?</p>