Set up 80 column indicator in Emacs

 1. Downalod "fill-column-indicator.el" into "~/.emacs.d/listp/"

 2. Put the following commands in .emacs
(require 'fill-column-indicator)
(setq-default fci-rule-column 80)
(setq fci-rule-width 1)
(setq fci-rule-color "grey80")
(setq-default fci-rule-character-color "green")
(add-hook 'after-change-major-mode-hook 'fci-mode)