Rails 3: “field-with-errors” wrapper changes the page appearance. How to avoid this?

Default ActionView::Base.field_error_proc. Its currently defined  within ActionView::Base: 

@@field_error_proc = Proc.new{ |html_tag, instance|
   "<div class=\"field_with_errors\">#{html_tag}</div>".html_safe
}

Using class inside config/application.rb:

config.action_view.field_error_proc = Proc.new { |html_tag, instance| 
   html_tag
}

The div element is a block element. Add style  CSS file to make it inline element:

.field_with_errors { display: inline; }

Follow this command: 

ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
   class_attr_index = html_tag.index 'class="'
 
   if class_attr_index
    html_tag.insert class_attr_index+7, 'error '
   else
    html_tag.insert html_tag.index('>'), ' class="error"'
  end
end