<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<style type="text/css">
#redOne {
width: 0;
height: 0;
border-left: 10px solid transparent;
border-right: 10px solid transparent;
border-bottom: 20px solid red;
} #greenOne {
width: 0;
height: 0;
border-left: 10px solid transparent;
border-right: 10px solid transparent;
border-top: 20px solid green;
} </style>
</head>
<body>
<div id="redOne"></div>
<div id="greenOne"></div> </body>
</html>
https://segmentfault.com/a/1190000002454383