Новая версия:
Код:

javascript: (function() { var style = "a { color: #00e !important; background: #ffc !important; outline: 1px solid #f90 !important; text-decoration: none !important; }\n" + "a:visited { color: #55e !important; background: #ffc !important; text-decoration: none !important; }\n" + "a:hover { background: #ffa !important; text-decoration: underline !important; }"; var styleId = "__customStyleLinks"; function addStyle(win) { var doc = win.document; var head = doc.getElementsByTagName("head"); if(!head.length) return; head = head[0]; var stlIt = doc.getElementById(styleId); if(!stlIt) { var stl = doc.createElement("style"); stl.type = "text/css"; stl.id = styleId; stl.appendChild(doc.createTextNode(style)); head.appendChild(stl); } else head.removeChild(stlIt); } function parseWin(win) { try { addStyle(win); } catch(e) {}; for(var i = 0, len = win.frames.length; i < len; i++) try { parseWin(win.frames[i]); } catch(e) {}; } parseWin(window); })();