<!DOCTYPE HTML>
<html>
<head>
<meta charset="gbk" />
<style type="text/css">
*{margin:0;padding:0;}
body{background:#000;}
.artItLaCorner {
width:20px;
border-color: transparent #fff;
border-style: solid;
border-width: 8px 7px 8px 0px;
margin: 4px 0px 0px 0px;
}
</style>
</head>
<body>
<div class="artItLaCorner"></div>
</body>
</html>
其他方向的根据自己需求去改变border-width。