These links seem to be dead. So here's my quick fix. All you need is something like [CJS Chrome Extension][1] (there are different ones for FF and Saf too!)

Then just inject code:

	;;(function($) {
		function z() {
			var a = $(window).scrollTop(),
				b = $(".topbar").height();
			a > b ? ($(".topbar").css({ position: "fixed", top: 0, "z-index": 999 }), $("body > .container").css({ "margin-top": b })) 
				: ($(".topbar").css({ position: "", top: "", "z-index": "" }), $("body > .container").css({ "margin-top": "" }))
		}
		if (document.readyState == "complete") z();
		else $(window).on('load', z);
		$(window).on("scroll", function(a) {
			this.tmr && clearTimeout(this.tmr);
			this.tmr = setTimeout(z, 10)
		});
	})(jQuery)

  [1]: https://chrome.google.com/webstore/detail/custom-javascript-for-web/ddbjnfjiigjmcpcpkmhogomapikjbjdk?hl=en