CSS

.verify-upsell {
  margin-top: 2em;
  padding-top: 1em;
  border-top: 1px solid #ccc;
  color: #aaa;
}

.verify-upsell h4 { 
  font-size: small;
  color: #aaa;
}

HTML

<div class="grid_12 download-pandas">
  <div class="grid_4 alpha"><img src="/static/images/panda-list.png" alt=""></div>
  <div class="grid_4"><img src="/static/images/panda-question.png" alt=""></div>
   <div class="grid_4 omega"><img src="/static/images/panda-wave.png" alt=""></div>
</div>

<!-- new stuff starts here -->

<div class="grid_12 verify-upsell">
<h4>Verifying Your Download</h4>
Please visit our <a href="#">download verification page</a> if you would like to verify the contents of your download for security and integrity.
</div>

<!-- new stuff ends -->