(let ((invisible-list '(navi2ch-article-header-face
			navi2ch-article-message-separator-face
			navi2ch-article-header-contents-face
			navi2ch-article-header-fusianasan-face))
      (beg nil)
      (end (point-min))
      (buffer-read-only nil)
      (inv nil))
  (when (memq (get-text-property (point-min) 'face)
	      invisible-list)
    (setq beg (point-min))
    (while (setq end (next-single-property-change end 'face))
      (when beg
	(add-text-properties beg end `(invisible ,inv)))
      (setq beg (and (memq (get-text-property end 'face)
			   invisible-list)
		     end)))))