header {position: fixed; left: 50%; margin-left: -50%;width: 100%;height: 6rem;border-bottom: 1px solid #f1f1f1; background: #fff; z-index: 100;}
header h1 {}
header h1 a {padding: 2rem 0; text-align: center; display: block; font-size:2.5rem; font-weight: bold;}