body { font-family: Arial; margin: 0; padding: 0; }
header { background: #333; color: #fff; padding: 10px; }
header nav a { color: white; margin: 0 5px; text-decoration: none; }
main { padding: 15px; }
table { width: 100%; border-collapse: collapse; margin-top: 10px; }
th, td { padding: 5px; border: 1px solid #ccc; }
.error { background: red; color: white; padding: 5px; margin-bottom: 10px; }