themes/bootstrap-2/views/articles/_comment_form.html.erb
<%= form_tag @article.comment_url do %>
<div id='commentform'>
<h3><%= t('.comment') %> <em><%= @article.title %></em></h3>
<div class='form-group'>
<%= text_field 'comment', 'author', class: 'form-control', placeholder: t('.your_name') %>
</div>
<div class='form-group'>
<%= text_field 'comment', 'email', class: 'form-control', placeholder: t('.email_address') %>
</div>
<div class='form-group'>
<%= text_field 'comment', 'url', class: 'form-control', placeholder: t('.your_website') %>
</div>
<div class='form-group'>
<%= text_area 'comment', 'body', rows: 8, class: 'form-control' %>
</div>
<% if this_blog.use_recaptcha %>
<div class='form-group'><%= raw recaptcha_tags ajax: true %></div>
<% end %>
<div class='form-actions'>
<input type='submit' id='form-submit-button' class='btn btn-info' value="<%= t('.comment') %>" />
</div>
</div>
<% end %>