Leave menu bar fixed on top when scrolled

This effect is typically achieved by having some jquery logic as follows:

$(window).bind('scroll', function () {
    if ($(window).scrollTop() > 50) {
        $('.menu').addClass('fixed');
    } else {
        $('.menu').removeClass('fixed');
    }
});

This says once the window has scrolled past a certain number of vertical pixels, it adds a class to the menu that changes it's position value to "fixed".

For complete implementation details see: http://jsfiddle.net/adamb/F4BmP/