                        課程
                    
                        /前端開發
                        
                            /JavaScript
                        
                        /形形色色的下拉菜單

為什么點其他二級菜單，三級菜單也顯示

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>無標題文檔</title>
<style>
?
?#nav{
??width: 600px;
?????? list-style: none;
??border: dashed 2px red;
??width: 600px;
??height: 80px;
??text-align: center;
??margin: 0 auto;
??
?}
?
?#nav li{
??float: left;
??width: 80px;
?}
?#nav li ul{
??list-style: none;
??padding: 0 80px;
?}
?#nav li a{
??line-height:80px;
??text-decoration: none;
??display: block;
??background-color: orange;
??text-align: center;
??
?}
?
?#nav li ul{
??display: none;
??position: relative;
??left:-80px;
?}
?#nav li:hover ul{
??display: block;
?}?

?
?#nav li:hover ul li ul{
??display: none;
??
??}
?#nav li ul li:hover ul? {
??display:block;
??position: absolute;
??top: 0;
??left: 80px;
?}
?</style>
</head>
<div >
?<ul id="nav">
??<li><a href="#">首頁+</a>
??<ul>
???<li><a href="#">css+</a>
???<ul>
????<li><a href="#">bbb</a></li>
????<li><a href="#">aaa</a></li>
???</ul></li>
???<li><a href="#">bcc</a>
???<ul>
????<li><a href="#">aaa</a></li>
????<li><a href="#">bbb</a></li>
???</ul></li>
???</li>
??</ul>
??</li>
??<li><a href="#">課程大廳</a></li>
??<li><a href="#">學習中心</a></li>
??<li><a href="#">關于我們</a></li>
?</ul>
</div>
<body>
</body>
</html>