nav{background:#222;position:sticky;top:0;}nav a{color:white;padding:10px;display:inline-block;text-decoration:none;font-size:20px;}h1, h2, h3, h4{text-align:center;padding:5px;color:white}h1{background:black}h2{background:green}h3{background:#033}h4{background:grey;}h3 a{text-decoration:none;color:yellow;} em{color:orange