h1 { font-size: 24px; font-weight: bold; } input { width: 200px; padding: 10px; border: 1px solid #ccc; } button { background-color: #000; color: #fff; padding: 10px; border: none; cursor: pointer; } .container { width: 500px; margin: 0 auto; } .alert { background-color: #f0f0f0; padding: 20px; margin: 0 auto; width: 400px; } function showAlert() { const alert = document.querySelector(".alert"); alert.style.display = "block"; } document.querySelector("form").addEventListener("submit", function() { showAlert(); });