can error_message_on display multiple errors?

Is there an easy way to make error_message_on display more than just
one error message? I know I could create a custom form builder, but it
looks complicated and I would rather learn that when I have more time.

for anyone else who might come across this, i found field_error_proc.
you can over ride it and have it automatically add the errors, you can
leave the error_message_on out of your code completely. you just add
this code to an initializer.

i combined it with the second example to also stop rails from putting
those annoying divs around the fields with errors, it makes much more
sense to simply add a css class to the fields.

http://snippets.dzone.com/posts/show/1671

ActionView::Base.field_error_proc = Proc.new {|html_tag, instance|
  if instance.error_message.kind_of?(Array)
    %(#{html_tag}<span class='validation-error'>&larr;#
{instance.error_message.join(',')}</span>)
  else
    %(#{html_tag}<span class='validation-error'>&larr;#
{instance.error_message}</span>)
  end
  }

http://thewebfellas.com/blog/2008/4/21/error-fields-with-a-hpricot-twist

ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
  if html_tag =~ /<(input|label|textarea|select)/
    error_class = 'error'
    nodes = Hpricot(html_tag)
    nodes.each_child { |node| node[:class] = node.classes.push
(error_class).join(' ') unless !node.elem? || node[:type] == 'hidden'

node.classes.include?(error_class) }

    nodes.to_html
  else
    html_tag
  end
end