anchor.diff:  <h1>Categorie di libri</h1>
   
  -<%= form_for :category, url: {action: 'create'} do |f| %>
   <table border="1">
   
     <thead>
  
positive.code: 
  
    <tr>
      <td>
        &nbsp;
      </td>
  
negative.code:     <td>
        <%= f.submit('+') %>
      </td>
      <% end %>
    </tr>
    </tbody>
  
  
  </table>
  
  
  
  
  