WordPress返回顶部、查看评论、转到底部代码

<script type="text/javascript" src="<?php bloginfo('template_directory');?>/js/jquery.js"></script>
<script type="text/javascript" src="<?php bloginfo('template_directory');?>/js/roll.js"></script>
<div id="roll">
       <div id="roll_up" title="↑ 返回顶部"></div>
       < ?php if ( is_singular() ){ ?>
       <div id="roll_comment" title="查看评论"></div>
       < ?php } ?>
       <div id="roll_down" title="↓ 移至底部"></div>
</div>

jQuery(document).ready(function($) {
    $body = (window.opera) ? (document.compatMode == "CSS1Compat" ? 
    $("html") : $("body")) : $("html,body");
    $("#roll_up").mouseover(function() {
        up()
    }).mouseout(function() {
        clearTimeout(fq)
    }).click(function() {
        $body.animate({
            scrollTop: 0
        },
        400)
    });
    $("#roll_down").mouseover(function() {
        dn()
    }).mouseout(function() {
        clearTimeout(fq)
    }).click(function() {
        $body.animate({
            scrollTop: $(document).height()
        },
        400)
    });
    $("#roll_comment").click(function() {
        $body.animate({
            scrollTop: $("#comment").offset().top
        },
        400)
    });
});
function up() {
    $wd = $(window);
    $wd.scrollTop($wd.scrollTop() - 1);
    fq = setTimeout("up()", 50)
};
function dn() {
    $wd = $(window);
    $wd.scrollTop($wd.scrollTop() + 1);
    fq = setTimeout("dn()", 50)
};

#roll{position:fixed; top:40%;left:50%;display:block;
margin-left:190px;z-index:999;width: 15px;height: 240px;_display:none;}
#roll_up,#roll_comment,#roll_down{position:relative;cursor:pointer;height:100px;width:15px;}
#roll_up{background:url(images/roll.png) no-repeat;}
#roll_comment{background:url(images/roll.png) no-repeat 0 -100px;height: 40px;}
#roll_down{background:url(images/roll.png) no-repeat 0 -140px;}