不设置宽度，直接设置padding。
<!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=utf-8" /> <title>自适应宽度菜单</title> <style type="text/css"> .header{ width: 880px; margin:0 auto; position: relative; } .nav{ position: absolute; top:130px; left: 0px; } .nav li{ float: left; list-style-type: none; } .nav a{ font-size: 14px; line-height: 1.5em; color: #555; padding:0 10px; text-decoration: none; } </style> </head> <body> <div class="header"> <div class="nav"> <li> <a href="#">博客园</a> </li> <li> <a href="#">首页</a> </li> <li> <a href="#">博问</a> </li> <li> <a href="#">闪存</a> </li> <li> <a href="#">新随笔</a> </li> <li> <a href="#">联系</a> </li> <li> <a href="#">订阅</a> </li> <li> <a href="#">管理</a> </li> </div> </div> </body> </html>
原文：http://www.cnblogs.com/alexandra/p/3526575.html