http://myeducs.cn/shejixiazai/wangye-template/DIV-buju-skill/CSS-wutushixianxiaosanjiaoxiaoguo/
CSS代码
<style type="text/css"><!--*{margin:0;padding:0;}#nav {width:150px;font-size:14px;margin:20px auto;border:1px solid #aaa;}#nav ul{list-style:none;}#nav li a{display:block;position:relative;text-align:center;text-decoration:none;color:#000;padding:5px;border:1px solid #fff;}#nav li a:hover{border:1px solid red;}span{width:0;height:0;overflow:hidden;border:6px solid #fff;}#nav li a:hover span.left{position:absolute;top:5px;left:10px;border-left-color:red;}#nav li a:hover span.right{position:absolute;top:5px;right:10px;border-right-color:red;}--></style>
HTML代码
<div ></span></a></li></ul></div>
http://jingyan.baidu.com/article/2c8c281d1524f70008252a2e.html
http://www.xpzhu.com/index.php/article/view/id/22