title: Positioning an image behind a centered div
body: <p>My site has a 900px div <code>#content</code> that is centered with <code>margin-left: auto</code> and <code>margin-right: auto</code>. I have an image that I need to display behind the div which will partially overlap <code>#content</code>.</p>
  
  <p>The image is set to display as block at present and I can get it to where it needs to be, but it doesn't allow <code>#content</code> to draw over the image. I can get <code>#content</code> to display over the image with <code>position: absolute</code> however this prevents the use of margin-left / margin-right auto to center.</p>
  
  <p>My current positioning, which gets it where it needs to be is:</p>
  
  <pre><code>img#watermark  
  {
      margin-left: auto;  
      margin-right: auto;
      display: block;
      padding-left: 900px;
  }
  </code></pre>
  
  <p><code>#content</code> just needs to appear over the watermark.</p>
  
  <p>Help greatly appreciated.</p>