三角形的css写法

<!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>
div {
    width: 0;
    height: 0;
    border-top: 40px solid #ff0000;
    border-left: 10px solid transparent;
    border-right: 5px solid transparent;
}
</style>
</head>

<body>
<div></div>
</body>
</html>
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原文地址：https://www.cnblogs.com/vscss/p/5619715.html