jQuery实现首次点击带动画效果的TAB切换

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>网页TAB代码</title>
<script type="text/javascript" src="jquery1.3.2.js"></script>
<style type="text/css">
body,h1,div,ul,li{ margin:0; padding:0;}
li{ list-style:none;}
.demo{ width:300px; margin:30px auto; position:relative;}
.demo li{ float:left; padding:0 15px; cursor:pointer; height:30px; line-height:30px;}
.d-bk{}
.demo li.cur{ background-color:#F00; color:#FFF;}
.demo li.cur .d-bk{ border:1px solid #F00; width:300px; height:150px; background-color:#f1f1f1; position:absolute; left:0; top:30px; color:#333;}
</style>
<script type="text/javascript">
 $(document).ready(function(){
  $(".demo li div").hide();
  $(".demo li").click(function(){
   $(this).addClass("cur").siblings().removeClass("cur");
   $("div.d-bk").slideDown()
   },function(){
   $("div.d-bk").slideUp() 
  })
 })
</script>
</head>
<body>
<ul class="demo">
 <li>
  导航1
 <div class="d-bk">111</div>
 </li>
 <li>
  导航2
 <div class="d-bk">222</div>
 </li>
 <li>
  导航3
 <div class="d-bk">333</div>
 </li>
</ul>
</body>
</html>