// ==UserScript==
// @name          Subpixel
// @namespace     https://github.com/tuxracer/subpixel
// @description   Restore subpixel anti-aliasing
// @downloadURL   https://raw.github.com/tuxracer/subpixel/master/subpixel.user.js
// @version       1.0.1
// @match         http://*/*
// @match         https://*/*
// ==/UserScript==

var headEl = document.querySelector('head')
  , styleEl = document.createElement('style')
  , styleTextNode = document.createTextNode('* { -webkit-font-smoothing: subpixel-antialiased !important; }')
  ;

styleEl.appendChild(styleTextNode);
headEl.appendChild(styleEl);

@@ -247,17 +247,17 @@
     1.0.
-1
+2
 %0A// @mat
@@ -533,16 +533,55 @@
 ')%0A  ;%0A%0A
+if (typeof headEl !== 'undefined') %7B%0A  
 styleEl.
@@ -608,16 +608,18 @@
 tNode);%0A
+  
 headEl.a
@@ -639,8 +639,10 @@
 yleEl);%0A
+%7D%0A

Check for head element