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<html lang="en"><head> <meta charset="UTF-8"> <title>Document</title> <script type="text/javascript" src="js/jquery-1.8.3.min.js"></script> <style> .active{ border-bottom: 3px solid #4b4; } ul{ height:80px; border: 1px solid #ddd; font-size:0; } ul li{ display: inline-block; height:50px; width:90px; text-align: center; line-height: 50px; color:#333; border-bottom: 3px solid #ccc; margin: 0px; padding: 0px; font-size:16px; font-family: "Microsoft YaHei",sans-serif; } </style> <script> $(function(){ var lis=$("li"); $.each(lis,function(i){ $(lis[i]).mouseenter(function(e){ $(".active").removeClass('active'); $(this).addClass('active'); }); }); }); </script></head><body> <ul> <li class="active">首页</li> <li>第一页</li> <li>第二页</li> <li>第三页</li> </ul></body></html>