描述：鼠标经过上面的某一个栏目的时候，该栏目的上面的边框会变为红色加粗，而且下面的内容区域也会随着顶部的改变而改变。所有的改变均通过类名来实现（添加或者删除类）。jquery的版本是1.8
实现代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>tab栏的切换</title>
<style>
* {
margin: 0;
padding: 0;
}
ul {
list-style: none;
}
.wrapper {
width: 1000px;
height: 475px;
margin: 0 auto;
margin-top: 100px;
}
.tab {
border: 1px solid #ddd;
border-bottom: 0;
height: 36px;
width: 320px;
}
.tab li {
position: relative;
float: left;
width: 80px;
height: 34px;
line-height: 34px;
text-align: center;
cursor: pointer;
border-top: 4px solid #fff;
}
.tab span {
position: absolute;
right: 0;
top: 10px;
background: #ddd;
width: 1px;
height: 14px;
overflow: hidden;
}
.products {
width: 1002px;
border: 1px solid #ddd;
height: 476px;
}
.products .main {
float: left;
display: none;
}
.products .main.selected {
display: block;
}
.tab li.active {
border-color: red;
border-bottom: 0;
}
</style>
<script src="../jquery.min.js"></script>
<script>
$(window).ready(function () {
$(".tab>li").mouseenter(function () {
$(this).addClass("active").siblings("li").removeClass("active");
$(".products>div").eq($(this).index()).addClass("selected").siblings("div").removeClass("selected");
});
});
</script>
</head>
<body>
<div class="wrapper">
<ul class="tab">
<li class="tab-item active">国际大牌<span>◆</span></li>
<li class="tab-item">国妆名牌<span>◆</span></li>
<li class="tab-item">清洁用品<span>◆</span></li>
<li class="tab-item">男士精品</li>
</ul>
<div class="products">
<div class="main selected">
<a href="###"><img src="images/guojidapai.jpg" alt=""/></a>
</div>
<div class="main">
<a href="###"><img src="images/guozhuangmingpin.jpg" alt=""/></a>
</div>
<div class="main">
<a href="###"><img src="images/qingjieyongpin.jpg" alt=""/></a>
</div>
<div class="main">
<a href="###"><img src="images/nanshijingpin.jpg" alt=""/></a>
</div>
</div>
</div>
</body>
</html>