def thumbnail_holder(span = 12, options = {}, &block)
      content_tag('li', nil, merge_predef_class("span#{span}", options)) do
        capture(&block) if block_given?
      end
    end
def thumbnail_holder(span = 12, options = {}, &block)
      content_tag('li', nil, merge_predef_class("span#{span}", options)) do
        capture(&block) if block_given?
      end
    end
Public: Thumbnail holders, represented by li, used in thumbnails helper.

 span    - Integer. Width of thumbnail, 1-12. ( default: 12 )
 options - Options can be accepted by li.
 block   - The content of thumbnail holder, usually is a thumbnail.

 Examples
   See thumbnails helper.