gistfile1.rb

  FIELDS = [:about_url, :feedback_url, :terms_of_service_url, :privacy_policy_url, :support_url, :contact_url]

  self.with_options(:with => /^(http|https):\/\/[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,5}(([0-9]{1,5})?\/.*)?$/ix ) do |url|
    FIELDS.each do |field|
      url.validates_format_of field, :if => lambda{ |val| !val.send(field).blank? }
    end
  end