Rails URL Validation (See related posts)

  validates_each :href, :on => :create do |record, attr, value|
    begin
      uri = URI.parse(value)
      if uri.class != URI::HTTP
        record.errors.add(attr, 'Only HTTP protocol addresses can be used')
      end
    rescue URI::InvalidURIError
      record.errors.add(attr, 'The format of the url is not valid.')
    end
  end