title: Mask div using CSS
body: <p>Ok so say i'm using the follow setup for my divs:</p>
  
  <p><code>.background</code> will contain an image.
  <code>.overlay</code> will have a semitransparent white background for the overlay
  <code>.inner</code> would effectively mask out a rectangle the size of the div? So that the background is transparent and cuts through the overlay div. </p>
  
  <pre><code>&lt;div class="background"&gt;
      &lt;div class="overlay"&gt;
          &lt;div class="inner"&gt;
          &lt;/div&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Is this possible with just css?</p>