1 <!DOCTYPE html>
2 <html lang="en">
3
4 <head>
5 <meta charset="UTF-8">
6 <meta name="viewport" content="width=device-width, initial-scale=1.0">
7 <meta http-equiv="X-UA-Compatible" content="ie=edge">
8 <meta name="author" content="杨欣">
9 <title>css三角形</title>
10 <style>
11 .triangle{
12 width: 0;
13 height: 0;
14 border-width: 40px;
15 border-style: solid;
16 border-color: transparent transparent transparent red;
17 /*border-color的四个值代表上右下左，分别实现下左上右箭头 */
18 }
19 </style>
20 </head>
21
22 <body>
23 <div class="triangle"></div>
24 </body>
25
26 </html>
来源：https://www.cnblogs.com/samsara-yx/p/10514697.html