title: How can I display an image using the "em" unit?
body: <p>I've created a <code>&lt;div&gt;</code> with <code>width:10em</code> and <code>height:5em</code>.<br>
  Now I would like to display an <code>&lt;img&gt;</code> (GIF image) in this <code>&lt;div&gt;</code> with the exact same size.
  But apparently it doesn't "know" the <code>em</code> unit. It shows the picture in 10x5 <em>pixels</em> instead.</p>
  
  <p>How can I display this <code>&lt;img&gt;</code> using the "em" unit?</p>