title: Make an empty <div> collapse, with a width and margin
body: <p>I consider myself a beginner at HTML, so sorry if this is a no-brainer.</p>
  
  <p>In the following example I'd like the 'LEFT' DIV to collapse when it is empty. However with BOTH the 'width' AND the 'margin' present it will not collapse. If I remove either one from the style it collapses fine.</p>
  
  <pre><code>&lt;html&gt;
    &lt;head/&gt;
    &lt;body&gt;
      &lt;div&gt;
        &lt;div style="float:left; width:25%; margin:40px 0 40px 0" &gt;
          LEFT
        &lt;/div&gt;
        &lt;div style="float:left; margin:40px 0 40px 0"&gt;
          RIGHT
        &lt;/div&gt;
      &lt;/div&gt;
    &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>Any idea how I can make the "LEFT" DIV collapse if I remove the word "LEFT"?</p>
  
  <p>Thanks</p>
  
  <p>-John</p>