css三角形

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>三角形制作</title>
    <style type="text/css">
        h1 {
            position: relative;
            padding-left: 50px;
        }
        h1:after {
            content: '';
            display: inline-block;
            width: 0;
            height: 0;
            border: 20px solid transparent;
            border-top-color: #F00;
            position: absolute;
            left: 0px;
            top: 20px;
        }
    </style>
</head>
<body>
<h1>一级标题</h1>
</body>
</html>
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原文地址：https://www.cnblogs.com/-CLAY-/p/border.html