Reveal nofollow links on Stack Exchange

nofollow.user.js

// ==UserScript==
// @name        Reveal nofollow links on Stack Exchange
// @version     1.3
// @namespace   http://vyznev.net/
// @description Colors all links with rel=nofollow red on the Stack Exchange network. (Works on other sites too, if you edit the includes.)
// @author      Ilmari Karonen
// @license     ISC (http://opensource.org/licenses/ISC)
// @match       *://*.stackexchange.com/*
// @match       *://*.stackoverflow.com/*
// @match       *://*.superuser.com/*
// @match       *://*.serverfault.com/*
// @match       *://*.stackapps.com/*
// @match       *://*.mathoverflow.net/*
// @match       *://*.askubuntu.com/*
// @grant       none
// @run-at      document-start
// ==/UserScript==

// Yes, that's all there really is to it:
var css = 'a[rel*=nofollow] { color: red !important; }';

// Inject style into page:
var style = document.createElement('style');
style.textContent = css;

var parent = (document.head || document.documentElement);
if (parent) parent.appendChild(style);
else {
  // work-around for https://github.com/greasemonkey/greasemonkey/issues/2996
  var obs = new MutationObserver(function () {
    var parent = (document.head || document.documentElement);
    if (parent) { obs.disconnect(); parent.appendChild(style); }
  });
  obs.observe(document, {childList: true});
}