$.fn.followTo = function (pos) {
        var $this = this,
            $window = $(window);

        $window.scroll(function (e) {
            if ($window.scrollTop() > pos) {

                $this.css({
                    position: 'fixed',
                    top: 0
                });

            } else {
            	$this.removeAttr('style');
            }
        });
    };
    // Calling the function
    $('#div').followTo(50);