代码如下： HTML: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>下拉菜单，竖向</title> <style type="text/css" media="screen"> <!-- #Nav { /*Make the left border */ width: auto; float: left; border-left: 1px solid #777; } ul { margin: 0px; padding: 0px; list-style: none; /*display: inline;*/ } ul li { position: relative; width: 120px; float: left; } li ul { position: absolute; left: 0px; top: 23px; display: none; border-bottom: 1px solid #777; border-left: 0px; } ul li a { display: block; font-size: 12px; line-height: 22px; text-decoration: none; color: #333; background-color: #FFF; height: 22px; padding-left: 8px; border: 1px solid #777; border-left: 0px; } ul li ul li a { /* The border of main menus is different from the sub menus */ border: 1px solid #777; border-bottom: 0px; } a:hover { color: #F60; background-color: #EFEFEF; } /* Fix IE. Hide from IE Mac \*/ * html ul li { float: left; height: 1%; } * html ul li a { height: 1%; } /* End */ li:hover ul, li.over ul { display: block; } --> </style> <script language="javascript" type="text/javascript"> <!-- startList = function() { if (document.all && document.getElementById) { var menuRoot = document.getElementById("Menu"); for (var i = 0; i < menuRoot.childNodes.length; i++) { var node = menuRoot.childNodes[i]; if (node.nodeName == "LI") { node.onmouseover = function() { this.className += " over"; } node.onmouseout = function() { this.className = this.className.replace(" over", ""); } } } } } window.onload = startList; --> </script> </head> <body> <div id="Nav"> <ul id="Menu"> <li><a href="#">Home</a></li> <li><a href="#">About us</a> <ul> <li><a href="#">Brief</a></li> <li><a href="#">History</a></li> <li><a href="#">Awards</a></li> </ul> </li> <li><a href="#">Services</a> <ul> <li><a href="#">Sites</a></li> <li><a href="#">Hosts</a></li> <li><a href="#">E-mail</a></li> </ul> </li> <li><a href="#">Contact us</a> <ul> <li><a href="#">Asia</a></li> <li><a href="#">North American</a></li> <li><a href="#">Europe</a></li> </ul> </li> </ul> </div> </body> </html> 需要说明的是： 首先为了获得主菜单左侧的边框，我增加了一个 id="Nav" 的块元素，并且浮动在左侧（发现没有了这个浮动，不会出现边框）。等一下看看直接让 Menu 浮动在左侧会不会有。 然后对于子菜单的定位，同横向有些不同。 演示： 下拉菜单，纵向 下拉菜单，横向 菜单翻转图片效果