html代码如下：
css样式：
body{background:#faf7ef;}div{margin:20px auto}div.arrow-up { width:0px; height:0px; border-left:50px solid transparent; border-right:50px solid transparent; border-bottom:50px solid #ff0000; font-size:0px; line-height:0px;} div.arrow-down { width:0px; height:0px; border-left:50px solid transparent; border-right:50px solid transparent; border-top:50px solid #0000ff; font-size:0px; line-height:0px;} div.arrow-left { width:0px; height:0px; border-bottom:50px solid transparent; border-top:50px solid transparent; border-right:50px solid #008000; font-size:0px; line-height:0px;} div.arrow-right { width:0px; height:0px; border-bottom:50px solid transparent; border-top:50px solid transparent; border-left:50px solid #ffff00; font-size:0px; line-height:0px;} 作者：风雨后见彩虹
出处：http://www.cnblogs.com/moqiutao/
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