为什么之前对a:hover的样式定义影响了之后的其他div下的a:hover（下面css程序里倒数第二个样式定义），要如何消除？
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>电商分类导航</title>
<link rel="stylesheet" type="text/css" href="电商分类导航.css">
</head>
<body>
<div id="mainnavi">
<div id="topmnue">全部商品分类</div>
<ul>
<li><a href="#">图书、音像、数字商品</a><span></span>
<div>
<div>
<dl>
<dt><a href="#">电子书</a></dt>
<dd>
<a href="#">免费</a>
<a href="#">小说</a>
<a href="#">励志与成功</a>
<a href="#">婚姻/两性</a>
<a href="#">文学</a>
<a href="#">经管</a>
</dd>
</dl>
<dl>
<dt><a href="#">数字音乐</a></dt>
<dd>
<a href="#">通俗流行</a>
<a href="#">古典音乐</a>
<a href="#">摇滚说唱</a>
<a href="#">爵士蓝调</a>
<a href="#">乡村民谣</a>
<a href="#">有声读物</a>
</dd>
</dl>
<dl>
<dt><a href="#">音像</a></dt>
<dd>
<a href="#">音乐</a>
<a href="#">影视</a>
<a href="#">教育音像</a>
<a href="#">游戏</a>
</dd>
</dl>
<dl>
<dt><a href="#">文艺</a></dt>
<dd>
<a href="#">小说</a>
<a href="#">文学</a>
<a href="#">青春文学</a>
<a href="#">传记</a>
<a href="#">艺术</a>
</dd>
</dl>
<dl>
<dt><a href="#">人文社科</a></dt>
<dd>
<a href="#">历史</a>
<a href="#">心理学</a>
<a href="#">政治/军事</a>
<a href="#">国学/古籍</a>
<a href="#">哲学/宗教</a>
<a href="#">社会科学</a>
</dd>
</dl>
<dl>
<dt><a href="#">经管励志</a></dt>
<dd>
<a href="#">经济</a>
<a href="#">金融与投资</a>
<a href="#">管理</a>
<a href="#">励志与成功</a>
</dd>
</dl>
<dl>
<dt><a href="#">生活</a></dt>
<dd>
<a href="#">家教与育儿</a>
<a href="#">旅游/地图</a>
<a href="#">烹饪/美食</a>
<a href="#">时尚/美妆</a>
<a href="#">家居</a>
<a href="#">婚恋与两性</a>
<a href="#">娱乐/休闲</a>
<a href="#">健身与保健</a>
<a href="#">动漫/幽默</a>
<a href="#">体育/运动</a>
</dd>
</dl>
<dl>
<dt><a href="#">科技</a></dt>
<dd>
<a href="#">科普</a>
<a href="#">IT</a>
<a href="#">建筑</a>
<a href="#">医学</a>
<a href="#">工业技术</a>
<a href="#">电子/通信</a>
<a href="#">农林</a>
<a href="#">科学与自然</a>
</dd>
</dl>
<dl>
<dt><a href="#">少儿</a></dt>
<dd>
<a href="#">少儿</a>
<a href="#">0-2岁</a>
<a href="#">3-6岁</a>
<a href="#">7-10岁</a>
<a href="#">11-14岁</a>
</dd>
</dl>
<dl>
<dt><a href="#">教育</a></dt>
<dd>
<a href="#">教材</a>
<a href="#">中小学教辅</a>
<a href="#">考试</a>
<a href="#">外语学习</a>
</dd>
</dl>
<dl>
<dt><a href="#">其它</a></dt>
<dd>
<a href="#">英文原版书</a>
<a href="#">港台图书</a>
<a href="#">工具书</a>
<a href="#">套装书</a>
<a href="#">杂志/期刊</a>
</dd>
</dl>
</div>
<div>
<img src="right1.jpg" title="家电">
<img src="right2.jpg" title="小家电">
<div>
<dl>
<dt>推荐品牌</dt>
<dd><a href="#">美的官方旗舰店</a></dd>
<dd><a href="#">苏泊尔官方旗舰店</a></dd>
<dd><a href="#">九阳官方旗舰店</a></dd>
<dd><a href="#">东菱官方旗舰店</a></dd>
<dd><a href="#">小熊官方旗舰店</a></dd>
</dl>
</div>
</div>
</div>
</li>
<li><a href="#">家用电器</a></li>
<li><a href="#">手机、数码</a></li>
<li><a href="#">电脑、办公</a></li>
<li><a href="#">家居、家具、家装、厨具</a></li>
<li><a href="#">服饰内衣、珠宝首饰</a></li>
<li><a href="#">个护化妆</a></li>
<li><a href="#">鞋靴、箱包、钟表、奢侈品</a></li>
<li><a href="#">运动户外</a></li>
<li><a href="#">汽车用品</a></li>
<li><a href="#">母婴、玩具乐器</a></li>
<li><a href="#">食品饮料、酒类、生鲜</a></li>
<li><a href="#">营养保健</a></li>
</ul>
</div>
<script type="text/javascript" src="电商分类导航.js"></script>
</body>
</html>
*{
margin: 0;
padding: 0;
font-size: 14px;
font-family: Microsoft Yahei;
}
#mainnavi{
width: 222px;
border: solid 3px red;
position: relative;
z-index: 3;
}
#topmnue{
background: red;
font-size: 16px;
color: white;
padding-left: 20px;
padding-top: 10px;
padding-bottom: 10px;
line-height: 20px;
height: 20px;
}
ul{
list-style: none;
}
a{
display: block;
text-decoration: none;
color: black;
margin-left: 7px;
padding-bottom: 10px;
height: 20px;
line-height: 20px;
width: 222px;
}
#mainnavi ul li:hover{
border: solid 1px #DDD;
border-right: 0;
box-shadow: 0 0 8px #DDD;
-moz-box-shadow: 0 0 8px #DDD;
-webkit-box-shadow: 0 0 8px #DDD;
}
#mainnavi ul li:hover span{
display: inline-block;
background-color: white;
height: 31px;
width: 7px;
position: absolute;
top: 40px;
left: 215px;
z-index: 30;
}
#mainnavi ul li a:hover{
text-decoration: underline;
color: red;
font-weight: bold;
}
#mainnavi ul li:hover .submnue{
display: block;
}
.submnue{
position: absolute;
left: 220px;
top: 30px;
z-index: 4;
width: 800px;
border: solid 1px #DDD;
border-right: 0;
box-shadow: 0 0 8px #DDD;
-moz-box-shadow: 0 0 8px #DDD;
-webkit-box-shadow: 0 0 8px #DDD;
}
.left{
float: left;
width: 550px;
background-color: white;
}
.right{
float: left;
margin-left: 10px;
width: 240px;
}
.left dl{
display: block;
overflow: hidden;
border-bottom: solid 1px #ccc;
margin-left: 10px;
margin-top: 10px;
margin-bottom: 4px;
}
.left dl dt{
display: block;
float: left;
width: 60px;
text-align: right;
height: 22px;
margin-right: 10px;
}
.left dl dt a{
width: 60px;
height: 22px;
font-size: 11px;
font-weight: bold;
text-decoration: underline;
color: red;
}
.left dl dd{
display: block;
overflow: hidden;
}
.left dl dd a{
display: block;
float: left;
width: 60px;
height: 14px;
line-height: 14px;
font-size: 10px;
font-weight: none;
color: #737373;
text-decoration: none;
border-left: solid 1px #ccc;
margin-bottom: 8px;
padding: 4px;
}
.right .right_bottom dl dt{
font-weight: bold;
font-size: 12px;
color: red;
}
.right .right_bottom dl dd{
margin: 3px 0;
}
.right .right_bottom dl dd a{
color: #737373;
font-size: 10px;
line-height: 22px;
}
.right .right_bottom dl dd a:hover{
color: black;
font-weight: normal;
}
.right_bottom{
position: absolute;
bottom: 60px;
left: 570px;
}
