#id名 {
  width:296px;
  height:130px; //半分の高さ
  position:relative;
  overflow:hidden;
}

<style>  
ul {list-style:none;margin:0;padding:0;}
li {float:left;width:100px;line-height:25px;height:25px;margin:0;padding:0;text-align:center;}
li a {background:url(背景圖片) repeat 0 0;display:block;padding:5px 10px;color:#FFF;text-decoration:none;border-right:1px solid #FFF;}
</style>
<script type="text/javascript" src="jquery-1.3.2.js"></script>
<script type="text/javascript" src="jquery.bgpos.js"></script>
<script type="text/javascript">
$(document).ready(function() {
  $('li a')
    .css( {backgroundPosition: "-20px 35px"} ) //デフォルト時、背景画像を横-20px、縦35pxに指定。
    .mouseover(function(){
      $(this).stop().animate({backgroundPosition:"(-20px 94px)"}, {duration:500})
      //マウスオーバー時に縦位置94pxに0.5秒かけて移動
    })
    .mouseout(function(){
      $(this).stop().animate({backgroundPosition:"(40px 35px)"}, {duration:200, complete:function(){
      //マウスアウト時に横位置40px、縦位置35pxに2秒かけて移動
        $(this).css({backgroundPosition: "-20px 35px"})
        //移動完了後、元の位置に戻す
      }})
  })
});
</script>

<ul id="demo">
  <li><a href="#">Home</a></li>
  <li><a href="#">About</a></li>
  <li><a href="#">Contact</a></li>

  $('#a a')
    .css( {backgroundPosition: "-20px 35px"} )
    .mouseover(function(){
      $(this).stop().animate({backgroundPosition:"(-20px 94px)"}, {duration:500})
    })
    .mouseout(function(){
      $(this).stop().animate({backgroundPosition:"(40px 35px)"}, {duration:200, complete:function(){
        $(this).css({backgroundPosition: "-20px 35px"})
      }})
    })

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.js"></script>
<script type="text/javascript" src="jquery.easing.1.3.js"></script>
<script type="text/javascript" src="jquery.hoverIntent.minified.js"></script>
<script type="text/javascript" src="jquery.flashyNav.1.0.js"></script>

<script type="text/javascript">
$(function(){
  
  $('.nav1').flashyNav({
    rolloverColor: '#5400ff',  //the default color of the rollover element
    rolloverDuration: 1000,  //the default duration for the rollover
    easingMethod: 'easeInOutQuint'  //easing method used for animation
  });
  
  $('.nav2').flashyNav({
    rolloverColor: '#00d2ff',  //the default color of the rollover element
    rolloverDuration: 800,  //the default duration for the rollover
    easingMethod: 'easeOutBounce'  //easing method used for animation
  });

  $('.nav3').flashyNav({
    rolloverColor: '#a800ff',  //the default color of the rollover element
    rolloverDuration: 800,  //the default duration for the rollover
    easingMethod: 'easeOutElastic'  //easing method used for animation
  });
  
});
</script>

<style type="text/css">
  
  * {margin:0; padding:0}
  body {background: #000; color:#fff; margin:20px; font-family:Arial, Helvetica, sans-serif; font-size:11px}
  a {color:#fff}
  
  ul.nav {list-style:none; margin:20px; width:300px; font-size:10px; font-family:Arial, Helvetica, sans-serif; font-weight:bold}
  ul.nav li {position:relative; border-bottom:1px solid #333; display:block; height:30px; overflow:hidden}
  ul.nav li a {position:relative; color:#fff; text-decoration:none; display:block; height:20px; padding:10px 0 0 10px; z-index:100; text-transform:uppercase}
  
</style>