//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);

    }

});