//
//$(document).ready(function(){   
//        $("#scrollDiv").Scroll({line:4,speed:500,timer:1000,up:"btn1",down:"btn2"});   
//});
//
//<div id="scrollDiv">  
//<ul>  
//    <li>Line 1</li>  
//    <li>Line 2</li>  
//    <li>Line 3</li>  
//    <li>Line 4</li>  
//    <li>Line 5</li>  
//    <li>Line 5</li>  
//    <li>Line 6</li>
//</ul>  
//</div>   
//<span id="btn1">Prev</span>&nbsp;&nbsp;<span id="btn2">Back</span> 
(function($) {
    $.fn.extend({
        Scroll: function(opt, callback) {
            if (!opt) var opt = {};
            var _btnUp = $("#" + opt.up);
            var _btnDown = $("#" + opt.down);
            var timerID;
            var _this = this.eq(0).find("ul:first");
            var lineH = _this.find("li:first").height(),
                        line = opt.line ? parseInt(opt.line, 10) : parseInt(this.height() / lineH, 10),
                        speed = opt.speed ? parseInt(opt.speed, 10) : 500;
            timer = opt.timer
            if (line == 0) line = 1;
            var upHeight = 0 - line * lineH;
            var scrollUp = function() {
                _btnUp.unbind("click", scrollUp);
                _this.animate({
                    marginTop: upHeight
                }, speed, function() {
                    for (i = 1; i <= line; i++) {
                        _this.find("li:first").appendTo(_this);
                    }
                    _this.css({ marginTop: 0 });
                    _btnUp.bind("click", scrollUp);
                });

            }
            var scrollDown = function() {
                _btnDown.unbind("click", scrollDown);
                for (i = 1; i <= line; i++) {
                    _this.find("li:last").show().prependTo(_this);
                }
                _this.css({ marginTop: upHeight });
                _this.animate({
                    marginTop: 0
                }, speed, function() {
                    _btnDown.bind("click", scrollDown);
                });
            }
            var autoPlay = function() {
                if (timer) timerID = window.setInterval(scrollUp, timer);
            };
            var autoStop = function() {
                if (timer) window.clearInterval(timerID);
            };
            _this.hover(autoStop, autoPlay).mouseout();
            _btnUp.css("cursor", "pointer").click(scrollUp).hover(autoStop, autoPlay);
            _btnDown.css("cursor", "pointer").click(scrollDown).hover(autoStop, autoPlay);

        }
    })
})(jQuery);