//config
$float_speed=0; //milliseconds
$float_easing="easeOutQuint";
$fl_menu=$("#menu-top");

$(window).load(function() {
    menuPosition = $fl_menu.position().top;
	FloatMenu();
});

$(window).scroll(function () { 
	FloatMenu();
});

function FloatMenu(){
	var scrollAmount=$(document).scrollTop();
	var newPosition=menuPosition+scrollAmount;
	if($(window).height()<$fl_menu.height()){
		$fl_menu.css("top",menuPosition);
	} else {
		$fl_menu.stop().animate({top: newPosition}, $float_speed, $float_easing);
	}
}