body { font-family: Arial, sans-serif; background: #f4f4f4; margin: 0; padding: 0; }
header { background: #222; color: #fff; padding: 1em; display: flex; justify-content: space-between; align-items: center; }
nav { background: #444; color: #fff; padding: 0.5em; }
nav a { color: #fff; margin-right: 1em; text-decoration: none; }
main { padding: 2em; }
.error { color: red; margin-bottom: 1em; }
.user-info { font-size: 0.9em; }