<html> <head> <style> /* Your CSS code here */ body { background-color: #f2f2f2; } h1 { color: green; } </style> </head> <body> <h1>Hello, CodeMirror!</h1> <script> // Your JavaScript code here var message = "Hello from JavaScript!"; console.log(message); // Generating an error intentionally undefinedFunction(); </script> </body> </html>