<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <title>Centering an Element with CSS Auto Margin</title> <style> .container { width: 350px; height: 250px; background: purple; margin: 0 auto; } </style> </head> <body> <div class="container"> <h1>This is a heading</h1> <p>This is a paragraph.</p> </div> </body> </html>