jquery滚动条滚动效果，右侧固定的滚动条代码

//侧栏随动
var rollStart = $('.feed-mail'), //滚动到此区块的时候开始随动
rollSet = $('.search,.weibo,.group,.feed-mail,.tags'); //添加rollStart之前的随动区块

rollStart.before('<div class="da_rollbox" style="position:fixed;background-color:#fff;width:inherit;"></div>');
var offset = rollStart.offset(),objWindow = $(window),rollBox = rollStart.prev();
objWindow.scroll(function() {
if (objWindow.scrollTop() > offset.top){
if(rollBox.html(null)){
rollSet.clone().prependTo('.da_rollbox');
}
rollBox.show().stop().animate({top:0,paddingTop:15},400);
} else {
rollBox.hide().stop().animate({top:0},400);
}
});