The Rickroll blocker
// ==UserScript==
// @name Rickblock
// @include *
// @description The Rickroll blocker
// @run-at document-end
// @version 0.0.1.20151125001049
// @namespace https://greasyfork.org/users/12417
// ==/UserScript==
var links = document.getElementsByTagName("a");
for (var i in links)
{
var linkto = links[i].getAttribute("href");
var isrickroll = (linkto.indexOf("dQw4w9WgXcQ") !== -1);
if (isrickroll)
{
links[i].innerHTML = "(removed Rickroll)";
links[i].setAttribute("href", "#");
}
}