<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title></title> <style type="text/css"> * { margin: 0px; padding: 0px; } #nav { width: 500px; background-color: #737373; height: 40px; /*border-radius: 10px;*/ position: relative; margin: 0px auto; top: 0px; } .nav-container { width: 100%; height: 40px; position: absolute; } .banner { float: left; text-align: center; height: 40px; width: 20%; line-height: 40px; } .banner:hover { background-color: #00BFFF; cursor: pointer; } div ul { list-style: none; /*display: none;*/ background-color: blue; overflow: hidden; /*模拟height:auto时候的情况*/ max-height: 0px; transition: max-height 0.3s; /*多浏览器支持*/ -moz-transition: height 1s; -webkit-transition: height 1s; -o-transition: height 1s; } .banner:hover ul { /*display: block;*/ width: 100%; max-height: 160px; } div ul li { overflow: hidden; } div ul li:hover { background-color: red; } </style> </head> <body> <div class="nav-container"> <div id="nav"> <div id="nav-button-1" class="banner">第1个导航 <ul> <li>1</li> <li>2</li> <li>3</li> <li>4</li> </ul> </div> <div id="nav-button-2" class="banner">第2个导航 <ul> <li>1</li> <li>2</li> <li>3</li> </ul> </div> <div id="nav-button-3" class="banner">第3个导航 <ul> <li>1</li> <li>2</li> </ul> </div> <div id="nav-button-4" class="banner">第4个导航 <ul> <li>1</li> <li>2</li> <li>3</li> <li>4</li> <li>5</li> </ul> </div> <div id="nav-button-5" class="banner">第5个导航 <ul> <li>1</li> <li>2</li> <li>3</li> <li>4</li> <li>5</li> </ul> </div> </div> </div> </body> </html>