Formatting Rails form elements for Twitter Bootstrap error validation

application.rb

ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
 html = %(<div class="field_with_errors">#{html_tag}</div>).html_safe
 # add nokogiri gem to Gemfile
 elements = Nokogiri::HTML::DocumentFragment.parse(html_tag).css "label, input"
 elements.each do |e|
   if e.node_name.eql? 'label'
     html = %(<div class="clearfix error">#{e}</div>).html_safe
   elsif e.node_name.eql? 'input'
     if instance.error_message.kind_of?(Array)
       html = %(<div class="clearfix error">#{html_tag}<span class="help-inline">&nbsp;#{instance.error_message.join(',')}</span></div>).html_safe
     else
       html = %(<div class="clearfix error">#{html_tag}<span class="help-inline">&nbsp;#{instance.error_message}</span></div>).html_safe
     end
   end
 end
 html
end

your_controller.css.scss

// Place all the styles related to the YourController controller here.
// They will automatically be included in application.css.
// You can use Sass (SCSS) here: http://sass-lang.com/

form .clearfix:before, form .clearfix:after {
  display: inline;
}

Forked to https://gist.github.com/dustMason/5817510 for Zurb Foundation 4. This version removes the Nokogiri dependency and thus performs better.