anchor.diff:  
         <h1>MARKUP VALIDATION FOR <a href='<%= @url %>'><%= @url %></a></h1>
   
  -      <% if errors.length > 0 %>
  -        <h2><%= errors.length %> HTML ERRORS</h2>
  -        <div class="accordion">
  -        <% errors.group_by {|e| e.text}.sort_by {|t, e| e.length}.reverse.each do |text, errors| %>
  -          <h3><span class="label label-danger"><%= errors.length %></span> <%= CGI::escapeHTML(text.capitalize) %></h3>
  -          <div>
  -            <% if errors.first.explanation && errors.first.explanation.strip.length > 0 %>
  -              <div class="w3c_explanation"><%= errors.first.explanation.strip %></div>
  -            <% end %>
  -          </div>
  -        <% end %>
  -        </div>
  -      <% end %>
  -
  -      <hr />
  -
  -      <% if warnings.length > 0 %>
  -        <h2><%= warnings.length %> HTML WARNINGS</h2>
  -        <div class="accordion">
  -        <% warnings.group_by {|w| w.text}.sort_by {|t, w| w.length}.reverse.each do |text, warnings| %>
  -          <h3><span class="label label-warning"><%= warnings.length %></span> <%= CGI::escapeHTML(text.capitalize) %></h3>
  -          <div>
  -            <% if warnings.first.explanation && warnings.first.explanation.strip.length > 0 %>
  -              <div class="w3c_explanation"><%= warnings.first.explanation.strip %></div>
  -            <% end %>
  -          </div>
  -        <% end %>
  -        </div>
  -      <% end %>
  -
  -      <hr />
  -
  -      <% processed_pages = pages.select{|p| !p.exception} %>
  -      <% if processed_pages.size > 0 %>
  -        <h2>DETAILS PER PAGE</h2>
  -        <% processed_pages.each do |page| %>
  -          <div class='page'>
  -            <h3>
  -              <a href='<%= page.url %>'><%= page.url %></a>
  -              <span class="label label-danger"><%= "#{page.errors.length} errors" %></span>
  -              <span class="label label-warning"><%= "#{page.warnings.length} warnings" %></span>
  -            </h3>
  -
  -            <div class="accordion">
  -              <% page.errors.sort_by {|e| e.line.to_i}.each do |error| %>
  +      <ul class="nav nav-tabs">
  +        <li class="active"><a href="#urls">List of URLs</a></li>
  +        <li><a href="#errors"><%= errors.length %> HTML errors</a></li>
  +        <li><a href="#warnings"><%= warnings.length %> HTML warnings</a></li>
  +      </ul>
  +
  +      <div class="tab-content">
  +        <div class="tab-pane active" id="urls">
  +          <% processed_pages = pages.select{|p| !p.exception} %>
  +          <% if processed_pages.size > 0 %>
  +            <% processed_pages.each do |page| %>
  +              <div class='page'>
                   <h3>
  -                  <span class="label label-danger">ERROR</span>
  -                  <%= CGI::escapeHTML(error.text.capitalize) %>
  +                  <a href='<%= page.url %>'><%= page.url %></a>
  +                  <span class="label label-danger"><%= "#{page.errors.length} errors" %></span>
  +                  <span class="label label-warning"><%= "#{page.warnings.length} warnings" %></span>
                   </h3>
   
  -                <div>
  -                  <% if error.line && error.col %>
  -                    <span class="coordinates label">
  -                      LINE <%= error.line %>, COL <%= error.col %>
  -                    </span>
  -                  <% end %>
  -
  -                  <% if error.source && error.source.strip.length > 0 %>
  -                    <pre><code class="html"><%= error.source.strip %></code></pre>
  -                  <% end %>
  -
  -                  <% if error.explanation && error.explanation.strip.length > 0 %>
  -                    <div class="w3c_explanation"><%= error.explanation.strip %></div>
  +                <div class="accordion">
  +                  <% page.errors.sort_by {|e| e.line.to_i}.each do |error| %>
  +                    <h3>
  +                      <span class="label label-danger">ERROR</span>
  +                      <%= CGI::escapeHTML(error.text.capitalize) %>
  +                    </h3>
  +
  +                    <div>
  +                      <% if error.line && error.col %>
  +                        <span class="coordinates label">
  +                          LINE <%= error.line %>, COL <%= error.col %>
  +                        </span>
  +                      <% end %>
  +
  +                      <% if error.source && error.source.strip.length > 0 %>
  +                        <pre><code class="html"><%= error.source.strip %></code></pre>
  +                      <% end %>
  +
  +                      <% if error.explanation && error.explanation.strip.length > 0 %>
  +                        <div class="w3c_explanation"><%= error.explanation.strip %></div>
  +                      <% end %>
  +                    </div>
  +
                     <% end %>
                   </div>
   
  -              <% end %>
  -            </div>
  -
  -            <div class="accordion">
  -              <% page.warnings.sort_by {|w| w.line.to_i}.each do |warning| %>
  -                <h3>
  -                  <span class="label label-warning">WARNING</span>
  -                  <%= CGI::escapeHTML(warning.text.capitalize) %>
  -                </h3>
  -
  -                <div>
  -                  <% if warning.line && warning.col %>
  -                    <span class="coordinates label">
  -                      LINE <%= warning.line %>, COL <%= warning.col %>
  -                    </span>
  -                  <% end %>
  -
  -                  <% if warning.source && warning.source.strip.length > 0 %>
  -                    <pre><code class="html"><%= warning.source.strip %></code></pre>
  -                  <% end %>
  -
  -                  <% if warning.explanation && warning.explanation.strip.length > 0 %>
  -                    <div class="w3c_explanation"><%= warning.explanation.strip %></div>
  +                <div class="accordion">
  +                  <% page.warnings.sort_by {|w| w.line.to_i}.each do |warning| %>
  +                    <h3>
  +                      <span class="label label-warning">WARNING</span>
  +                      <%= CGI::escapeHTML(warning.text.capitalize) %>
  +                    </h3>
  +
  +                    <div>
  +                      <% if warning.line && warning.col %>
  +                        <span class="coordinates label">
  +                          LINE <%= warning.line %>, COL <%= warning.col %>
  +                        </span>
  +                      <% end %>
  +
  +                      <% if warning.source && warning.source.strip.length > 0 %>
  +                        <pre><code class="html"><%= warning.source.strip %></code></pre>
  +                      <% end %>
  +
  +                      <% if warning.explanation && warning.explanation.strip.length > 0 %>
  +                        <div class="w3c_explanation"><%= warning.explanation.strip %></div>
  +                      <% end %>
  +                    </div>
  +
                     <% end %>
                   </div>
  -
  -              <% end %>
  +              </div>
  +            <% end %>
  +          <% end %>
  +        </div>
  +
  +        <div class="tab-pane" id="errors">
  +          <% if errors.length > 0 %>
  +            <div class="accordion">
  +            <% errors.group_by {|e| e.text}.sort_by {|t, e| e.length}.reverse.each do |text, errors| %>
  +              <h3><span class="label label-danger"><%= errors.length %></span> <%= CGI::escapeHTML(text.capitalize) %></h3>
  +              <div>
  +                <% if errors.first.explanation && errors.first.explanation.strip.length > 0 %>
  +                  <div class="w3c_explanation"><%= errors.first.explanation.strip %></div>
  +                <% end %>
  +              </div>
  +            <% end %>
               </div>
  -          </div>
  -        <% end %>
  -      <% end %>
  +          <% end %>
  +        </div>
  +
  +        <div class="tab-pane" id="warnings">
  +          <% if warnings.length > 0 %>
  +            <div class="accordion">
  +            <% warnings.group_by {|w| w.text}.sort_by {|t, w| w.length}.reverse.each do |text, warnings| %>
  +              <h3><span class="label label-warning"><%= warnings.length %></span> <%= CGI::escapeHTML(text.capitalize) %></h3>
  +              <div>
  +                <% if warnings.first.explanation && warnings.first.explanation.strip.length > 0 %>
  +                  <div class="w3c_explanation"><%= warnings.first.explanation.strip %></div>
  +                <% end %>
  +              </div>
  +            <% end %>
  +            </div>
  +          <% end %>
  +        </div>
  +      </div>
   
         <hr />
   
  
positive.code: 
      </div>
  
      <script src="http://netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
  
      <script src="http://ajax.googleapis.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
      <script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.10.3/jquery-ui.min.js"></script>
      <script type="text/javascript">
        $('.accordion').accordion({active: 'false', heightStyle: 'content' });
      </script>
  
      <script src="https://sitevalidator.com/cdn/highlightjs/7.3/highlight.min.js"></script>
      <script type="text/javascript">
        hljs.initHighlightingOnLoad();
      </script>
    </body>
  </html>
  
negative.code: 
        a.navbar-brand { color: #FFF !important; }
  
        .tab-pane { padding-top: 10px; }
  
        /* Explanations */
        .w3c_explanation { border: 1px solid #ddd; background-color: #ffe; padding: 10px; margin: 5px 5px 25px 5px; font-size: 0.8em; }
        .helpwanted { float: right; font-size: 2em; }
  