CSS Mockups for Ads

Occasionally I need to mockup where the ads are going to go in an application (it has to pay for itself somehow, right?). Rather than putting the ads into the application while I am still doing development, I use some simple CSS to put a placeholder where the ads will go. In Rails, it looks like this:

<div class="ads vertical_tower">
  <% if RAILS_ENV == 'production' -%>
    <script>... Live Ad Code Goes Here </script>
  <% else -%>
    Ads Go Here
  <% end -%>
</div>

Then I can use my simple ad template CSS to make it standout. Check out the css source on Github