<html> <head> <meta charset="UTF-8"> <title>Untitled Page</title> <meta name="viewport" content="width=device-width, initial-scale=1"> <style> body { max-width: 100ch; margin: 0 auto; padding: 2em; line-height: 1.4em; } :target { background: palegoldenrod; } header::after { content: ""; display: block; border-top: 1px solid gray; } </style> </head> <body> <header> <h1>Untitled Page</h1> </header> <main> <article>This content is replaced.</article> </main> </body> </html>