body { font-family: Arial, sans-serif; margin:0; padding:0; }
header img.header-img { width:100%; height:auto; display:block; }
nav { background:#333; padding:10px; }
nav a { color:white; margin-right:15px; text-decoration:none; }
main { padding:20px; }
footer { background:#eee; padding:10px; text-align:center; margin-top:20px; }