field_error_proc

gistfile1.rb

ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
  unless html_tag =~ /^<label/
    unless html_tag =~ / type=(["'])(radio|chekbox)\1/
      %{<div class="field_with_errors">#{html_tag}<div class="error">#{instance.error_message.first}</div></div>}.html_safe
    end
  else
    html_tag
  end
end