<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Document</title> <style> .father{ border-color: red; border- 2px; border-style: solid; margin: 0 auto; margin-top: 50px; height: 200px; 400px; } .father .child{ margin: 0% auto; margin-top: 10%; 0px; height: 0px; border-left: 50px solid transparent; border-right: 50px solid transparent; border-top: 60px solid red; } </style> </head> <body> <div class="father"> <div class="child"></div> </div> </body> </html>