_side.html.erb

<div class="span3">
    <% if content_for?(:special_block) %>
      <%= yield :special_block %>
    <% else %>
      <div class="promote">
        <a href="/products/index.html" class="btn btn-info btn-large" id="special_discount">Special Discount! Only Today!</a>
      </div>
    <% end %>
    <div class="well sidebar-nav">
        <ul class="nav nav-list">
            <li class="nav-header">Search Engines</li>
            <li class="active"><a href="https://www.google.com/">Google</a></li>
            <li><a href="https://www.yahoo.com/">Yahoo!</a></li>
            <li><a href="http://www.bing.com/">Bing</a></li>
            <li><a href="http://www.ask.com/">Ask.com</a></li>
            <li class="nav-header">social networking websites</li>
            <li><a href="https://www.facebook.com/">Facebook</a></li>
            <li><a href="https://twitter.com/">Twitter</a></li>
            <li><a href="https://plus.google.com/">Google+</a></li>
            <li><a href="http://www.linkedin.com/">LinkedIn</a></li>
            <li><a href="http://www.flickr.com/">Flickr</a></li>
            <li><a href="https://foursquare.com/">Foursquare</a></li>
            <li><a href="http://delicious.com/">delicious</a></li>
            <li><a href="http://www.anobii.com/">aNobii</a></li>
        </ul>
    </div><!--/.well -->
</div><!--/span-->