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html, body, ul, li, h1, h2, h3, h4, h5, h6, fieldset, legend {padding:0; margin:0;}
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ul li{list-style-type:none;text-transform:capitalize;}
#nav .mainlevel{float:left;margin-right:20px;padding-right:3px;background:#ffff00;width:140px;text-align:center; line-height:22px;}
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<title>jquery下拉竖导航菜单代码</title>
</head>
<body>
<br /><br /><br />
<div id="menu">
<ul id="nav">
<li id="mainlevel_01" class="mainlevel">
<a href="#">第一</a>
<ul class="linHideStyle">
<li>
<a href="">the one</a>
</li>
<li>
<a href="">the one</a>
</li>
<li>
<a href="">the one</a>
</li>
</ul>
</li>
<li id="mainlevel_02" class="mainlevel">
<a href="#">第二</a>
<ul class="linHideStyle">
<li>
<a href="">the one</a>
</li>
<li>
<a href="">3333dd</a>
</li>
<li>
<a href="">the one</a>
</li>
</ul>
</li>
<li id="mainlevel_03" class="mainlevel">
<a href="#">第三</a>
<ul class="linHideStyle">
<li>
<a href="">the one</a>
</li>
<li>
<a href="">the one</a>
</li>
<li>
<a href="">the one</a>
</li>
</ul>
</li>
<li id="mainlevel_04" class="mainlevel">
<a href="#">第四季度</a>
<ul class="linHideStyle">
<li>
<a href="">the one</a>
</li>
<li>
<a href="">the one</a>
</li>
<li>
<a href="">the one</a>
</li>
</ul>
</li>
</ul>
</div>
</body>
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