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                        /JavaScript进阶篇

为什么对ul加上height就可以使上下两块分离，不加的话，ul就跑到了div框里？

<!DOCTYPE html>
<html>
<head ><lang="en"></lang>
    <meta charset="UTF-8">
    <title>实践题 - 选项卡</title>
    <style type="text/css">
     /* CSS样式制作 */ 
     /**
     cursor:pointer;手型光标
     **/
    *{margin:0;padding:0;font-size:14px;font-family:宋体;}
    #d{
        width:290px;height:150px;padding;10px;margin:20px;
    }
    #d ul{
        list-style:none;display:block;line-height:30px;height:1px;
    }
    #d ul li { 
        float:left;width:60px;height:30px;line-height:30px;margin:0px 3px ;border:1px solid gray;border-bottom:none;text-align:center;   cursor:pointer;   display:inline-block;
    } 
    #d ul li.on{
        border-top:2px solid #f11;border-bottom:2px solid #fff;
    }
    #d div{
        height:120px;line-height:25px;border:1px solid gray;border-top:2px solid #f11; padding:5px;margin-top:30px;
    }
    .hide{display:none;}
    li:hover{background-color:#f60;}
     
    </style>
    
    <script type="text/javascript">
         // JS实现选项卡切换
    window.onload=function(){
        var d=document.getElementById("d");
        var li=document.getElementsByTagName("li");
        var div=d.getElementsByTagName("div");

        for(var i=0;i<li.length;i++){
             li[i].index=i;
             li[i].onclick=function(){
                 for(var n=0;n<li.length;n++){
                     li[n].className="";
                     div[n].className="hide";
                 }
                 this.className="on";
                 div[this.index].className="";
             }
        }
      
    
    }
    </script>
  
</head>
<body>
<!-- HTML页面布局 -->
<div id="d">
    <ul>
       <li class="on">房产</li>       
       <li>家居</li>
       <li>二手房</li>
    </ul>
     <div>
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     <div class="hide"> 
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     <div class="hide"> 
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</div>
 
</body>
</html>