Debugger entered--Lisp error: (error "No file on this line")
  signal(error ("No file on this line"))
  error("No file on this line")
  dired-get-file-for-visit()
  (if (derived-mode-p (quote dired-mode)) (dired-get-file-for-visit) buffer-file-name)
  html-site-buffer-or-dired-file-name()
  (setq file (html-site-buffer-or-dired-file-name))
  (if file nil (setq file (html-site-buffer-or-dired-file-name)))
  (unless file (setq file (html-site-buffer-or-dired-file-name)))
  nxhtml-buffer-possibly-local-viewable()