Paste this into your address bar and/or your bookmark bar and you get a FPS counter on any site. Pretty useful if you lag or if you want to benchmark your browser. (Note that it's the same FPS counter used in OmniPlayer2.)
javascript:(function(){var script=document.createElement('script');script.type='text/javascript';script.src='http://github.com/mrdoob/stats.js/raw/master/build/Stats.js';document.body.appendChild(script);script=document.createElement('script');script.innerHTML='var interval=setInterval(function(){if(typeof Stats==\'function\'){clearInterval(interval);var stats=new Stats();stats.getDomElement().style.position=\'fixed\';stats.getDomElement().style.left=\'0px\';stats.getDomElement().style.top=\'0px\';document.body.appendChild(stats.getDomElement());setInterval(function(){stats.update();},1000/60);}},100);';document.body.appendChild(script);})();