1. <!DOCTYPE html>
    2. <html lang="en">
    3. <head>
    4.     <meta charset="UTF-8">
    5.     <meta name="viewport" content="width=device-width, initial-scale=1.0">
    6.     <title>Document</title>
    7. </head>
    8. <style>
    9.     div{
    10.         width: 0;
    11.         height: 0;
    12.         border: 15px solid transparent;
    13.         border-top-color: #333;
    14.     }
    15. </style>
    16. <body>
    17.     <div>
    18. </div>
    19. </body>
    20. </html>