Плавный скроллинг страницы

#scroller{
    position: fixed;    
    /** позиция кнопки scroll to top **/
    bottom: 30px;   
    /** картинка кнопки наверх**/
    background: transparent url("../images/arrow.png") no-repeat left top;  
    width: 32px;
    height: 32px;
    cursor: pointer;
    /** скрываем кнопку в начале **/
    display:none;
}

<script>
$(document).ready(function(){   
    $(window).scroll(function () {
        if ($(this).scrollTop() > 0) {
            $('#scroller').fadeIn();
        } else {
            $('#scroller').fadeOut();
        }
    });
    $('#scroller').click(function () {
        $('body,html').animate({
            scrollTop: 0
        }, 400);
        return false;
    });
});
</script>

<script src="http://dle-news.ru/templates/Default/js/application.js"></script>

<script src="{THEME}/js/jquery.nicescroll.min.js" type="text/javascript"></script>
    <script type="text/javascript">
    $(document).ready(function() {
            $("html").niceScroll({
                background: "#ccc",
                cursorwidth: 9,
                cursorborderradius: 0,
                cursoropacitymin: 1,
                scrollspeed: 74,
                mousescrollstep: 28,
                enablemousewheel: true,
                hidecursordelay: 100,
                cursorfixedheight: 80
            });
        }
    );
  </script>

</head>

<script src="http://cdnjs.cloudflare.com/ajax/libs/jquery/1.8.3/jquery.min.js" type="text/javascript" charset="utf-8"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/jquery-mousewheel/3.0.6/jquery.mousewheel.min.js" type="text/javascript" charset="utf-8"></script>
<script>
;(function($) {
    'use strict';
    
    $.srSmoothscroll = function(options) {
    
    var self = $.extend({
        step: 55,
        speed: 400
    }, options || {});
    
    // private fields & init
    var win = $(window),
        doc = $(document),
        top = 0,
        step = self.step,
        speed = self.speed,
        viewport = win.height(),
        body = $.browser.webkit ? $('body') : $('html'),
        wheel = false;

    // events
    $('body').mousewheel(function(event, delta) {

        wheel = true;

        if (delta < 0) // down
            top = (top+viewport) >= doc.height() ? top : top+=step;

        else // up
            top = top <= 0 ? 0 : top-=step;

        body.stop().animate({scrollTop: top}, speed, function () {
            wheel = false;
        });

        return false;
    });

    win
    .on('resize', function (e) {
        viewport = win.height();
    })
    .on('scroll', function (e) {
        if (!wheel)
            top = win.scrollTop();
    });
    
    };
})(jQuery);

$(function () {
    $.srSmoothscroll();
});
</script>