These links seem to be dead. So here's my quick fix. All you need is something like CJS Chrome Extension (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)

These links seem to be dead. So here's my quick fix. All you need is something like CJS Chrome Extension (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)

Or I made THIS