anchor.diff:  
   <table>
     <tr>
  +    <th></th>
       <th>名前</th>
       <th>緯度・経度</th>
       <th>URL</th>
  
positive.code:     <th>答3</th>
      <th>正解番号</th>
      <th>作成者</th>
      <th></th>
      <th></th>
    </tr>
  
  <% @landmarks.each do |landmark| %>
    <tr>
      <td><%= landmark.name %></td>
      <td><%= map_link(landmark) %></td>
      <td><%= link_to landmark.url, landmark.url, target: "_blank" %></td>
  
negative.code:     <td><%= landmark.answer3 %></td>
      <td><%= landmark.correct %></td>
      <td><%= landmark.author %></td>
    </tr>
  <% end %>
  </table>
  