UserCSS.js for Opera

usercss.js

// ==UserScript==
// @name UserCSS
// @include *
// ==/UserScript==

(function() {

  function userCSS(event) {
    [
      {
        url: "http://example.com/",
        css: "#side{display:none!important}"
      },
      {
        url: "http://example.org/",
        css: "body{font-size:80%!important}"
      }
    ].forEach(function(list) {
      if (location.href.indexOf(list.url) >= 0) {
        var style = document.createElement("style");
        style.textContent = list.css;
        document.head.appendChild(style);
      }
    });
  }

  opera.addEventListener("BeforeCSS", function(event) {
    opera.removeEventListener(event.type, arguments.callee, false);
    userCSS.apply(null, arguments);
    userCSS = function() {};
  }, false);

  addEventListener("DOMContentLoaded", function(event) {
    userCSS.apply(null, arguments);
    userCSS = function() {};
  }, false);

})();