body { font-family: Arial, sans-serif; background:#f4f4f4; margin:0; }
header, footer { background:#222; color:#fff; text-align:center; padding:15px; }
nav { background:#333; padding:10px; }
nav a { color:#fff; margin-right:15px; text-decoration:none; font-weight:bold; }
nav a:hover { text-decoration:underline; }
main { padding:20px; background:#fff; max-width:900px; margin:20px auto; box-shadow:0 0 5px rgba(0,0,0,0.2); }
img { margin:5px; }