How to hide last divider in list of comments using CSS?

I want to hide last divider between comments using css. Code is below.

<div id="question_comments" class="comments_container">
  <div class="comment">
    <div class="comment_details">
      <div>
        <p>Comment1</p>
      </div>
    </div>
  </div>
  <div class="hr-comment"></div>
  <div class="comment">
    <div class="comment_details">
      <div>
        <p>Comment2</p>
      </div>
    </div>
  </div>
  <div class="hr-comment"></div>
  <div id="question_comment">
    <form> ... </form>
  </div>
  <div class="clear"></div>
</div>

I am generating that in rails view:

<div id="question_comments" class="comments_container">
  <% @question.comments.order("created_at ASC").each do |comment| %>
    <%= render :partial => "questions/comment", :locals => { :comment => comment } %>
    <div class="hr-comment"></div>
  <% end %>
  <%= render :partial => 'new_comment', :locals => {:targit => @question, :answer => nil} %>
  <div class="clear"></div>
</div>

I tried that:

div.hr-comment {
  background:url(hr-background.gif) repeat-x;width:100%;height:2px;margin-top:7px;margin-bottom:7px;width:310px;
}

.hr-comment:last-child { 
    display: none 
}

Goal is how to do that without using ruby in view.

Solution

It's generally frowned upon to add extra markup like empty divs purely for styling purposes.

.comment + .comment:before {
    border-top:1px solid;
    max-width: 300px;
    margin: 0 auto;
    content: " ";
    display: block;
}

http://jsfiddle.net/pVcrV/1/

The adjacent selector has greater support in older browsers than pseudo classes like :last-child (not available in IE8) or :last-of-type. The :before psuedo class has fairly decent support (not available IE7).