<!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>无标题文档</title>
<style type="text/css">
.area {
margin:100px auto;
width:300px;
height: 150px;
}
.item {
float:left; clear:both;
margin-bottom:23px;
}
/* 向上的箭头 */
.dot-top {
font-size: 0;
line-height: 0;
border-width: 10px;
border-color: red;
border-top-width: 0;
border-style: dashed;
border-bottom-style: solid;
border-left-color: transparent;
border-right-color: transparent;
}
/* 向右的箭头 */
.dot-right {
font-size: 0;
line-height: 0;
border-width: 10px;
border-color: red;
border-right-width: 0;
border-style: dashed;
border-left-style: solid;
border-top-color: transparent;
border-bottom-color: transparent;
}
/* 向下的箭头 */
.dot-bottom {
font-size: 0;
line-height: 0;
border-width: 10px;
border-color: red;
border-bottom-width: 0;
border-style: dashed;
border-top-style: solid;
border-left-color: transparent;
border-right-color: transparent;
}
/* 向左的箭头 */
.dot-left {
font-size: 0;
line-height: 0;
border-width: 10px;
border-color: red;
border-left-width: 0;
border-style: dashed;
border-right-style: solid;
border-top-color: transparent;
border-bottom-color: transparent;
}
</style>
</head>
<body>
<div class="area">
<span class="item dot-top"></span>
<span class="item dot-right"></span>
<span class="item dot-bottom"></span>
<span class="item dot-left"></span>
</div>
</body>
</html>另外我后来发现通过设置不同方向边线宽度，还可以调整斜角的角度；修改bord-width的值，修改三角形的大小，这个很简单大家自己修改尝试下吧就不赘述啦
