put inside auctions/new.html.erb

gistfile1.rhtml

  <% if form.object.errors.any? %>
    <div id="error_explanation">
      <h2>The following errors prohibited this form from being saved:</h2>
      <ul>
        <% form.object.errors.full_messages.each do |message| %>
          <li><%= message %></li>
        <% end %>
      </ul>
    </div>
  <% end %>