一款基于jQuery的带文字标题上下切换焦点图

 <div class="i_box">
        <div class="i_imglist">
            <ul id="J_imgList">
                <li><a href="#">
                    <img src="images/a358be24367a5ea9dec7aa61a7527a7ab16009b9_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/c4e37762e79866a2f10d3c5926bbd188924ddbd3_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/c4e37762e79866a2f10d3c5926bbd188924ddbd3_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/8a37e5af175db41e06004dc098e9c173aee70116_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/61f4d9a7eb72c52d84b7d86abe75a85b96b52da8_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/b74aaf555eb970c3a1fdd6e7b2b5dd2a7a971286_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/156c2157ea31033cd8d2ae8431be8497387e5db0_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/4dc9209aafd33affd86dd6c5b21b9f013ae06b88_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/c4e37762e79866a2f10d3c5926bbd188924ddbd3_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/c4e37762e79866a2f10d3c5926bbd188924ddbd3_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/8a37e5af175db41e06004dc098e9c173aee70116_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/61f4d9a7eb72c52d84b7d86abe75a85b96b52da8_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/156c2157ea31033cd8d2ae8431be8497387e5db0_m.jpg" alt="" title="" /></a></li>
                <li><a href="#">
                    <img src="images/4dc9209aafd33affd86dd6c5b21b9f013ae06b88_m.jpg" alt="" title="" /></a></li>
            </ul>
        </div>
        <!--切换大图-->
        <div class="i_nav">
            <div class="i_navlist">
                <ul id="J_navList">
                    <li><a href="#">站长素材</a></li>
                    <li><a href="#">一直照进我心里</a></li>
                    <li><a href="#">往事已遥远</a></li>
                    <li><a href="#">一年又一年</a></li>
                    <li><a href="#">22风吹起的青色衣衫</a></li>
                    <li><a href="#">夕阳里的温暖容颜</a></li>
                    <li><a href="#">你比以前更加美丽</a></li>
                    <li><a href="#">像盛开的花</a></li>
                    <li><a href="#">33阳光真温暖</a></li>
                    <li><a href="#">一直照进我心里</a></li>
                    <li><a href="#">往事已遥远</a></li>
                    <li><a href="#">一年又一年</a></li>
                    <li><a href="#">44风吹起的青色衣衫</a></li>
                    <li><a href="#">夕阳里的温暖容颜</a></li>
                </ul>
            </div>
        </div>
        <!--图片导航-->
        <div class="i_prev" id="J_prev">
            <a href="javascript:void(0)">&lt;&nbsp;</a></div>
        <div class="i_next" id="J_next">
            <a href="javascript:void(0)">&nbsp;&gt;</a></div>
    </div>

 /*reset css*/
        *
        {
            margin: 0;
            padding: 0;
            list-style: none;
            border: 0;
        }
        /*demo css*/
        .i_box
        {
            position: relative;
            overflow: hidden;
            width: 700px;
            height: 350px;
            margin: 40px auto 0 auto;
        }
        .i_imglist
        {
            width: 700px;
            height: 350px;
            z-index: 0;
        }
        .i_imglist li img
        {
            width: 700px;
            height: 350px;
            display: block;
        }
        .i_nav
        {
            position: absolute;
            left: 20px;
            bottom: 0;
            overflow: hidden;
            width: 660px;
            height: 30px;
            z-index: 2;
        }
        .i_nav ul li
        {
            float: left;
            _display: inline;
            width: 163px;
            height: 30px;
            margin: 0 1px;
            background-color: #000;
            opacity: 0.5;
            filter: alpha(opacity=50);
            text-align: center;
            line-height: 30px;
            cursor: pointer;
        }
        .i_nav ul li.hover
        {
            background-color: #fff;
            opacity: 0.8;
            filter: alpha(opacity=80);
        }
        .i_nav ul li a
        {
            color: #fff;
            text-decoration: none;
        }
        .i_nav ul li a:hover
        {
            text-decoration: underline;
        }
        .i_nav ul li.hover a
        {
            color: #000;
        }
        .i_prev a, .i_next a
        {
            position: absolute;
            overflow: hidden;
            width: 19px;
            height: 30px;
            background-color: #000;
            color: #fff;
            text-align: center;
            font-weight: bold;
            opacity: 0.9;
            filter: alpha(opacity=90);
            text-decoration: none;
            line-height: 30px;
        }
        .i_prev a
        {
            left: 0;
            bottom: 0;
        }
        .i_next a
        {
            right: 0;
            bottom: 0;
        }
        .i_prev a:hover, .i_next a:hover
        {
            background-color: #fff;
            opacity: 0.8;
            filter: alpha(opacity=80);
            color: #000;
        }