.header{
    background-image: -webkit-gradient(linear, left bottom, left top, from(#f1503b), color-stop(50%, #c82519));
    background-image: -webkit-linear-gradient(bottom, #f1503b, #c82519 50%);
    background-image: linear-gradient(0deg, #f1503b, #c82519 50%);
    width: 100%;
    height: 190px;
    border-bottom-left-radius: 100%;
    border-bottom-right-radius: 100%;
}

.nav{
    margin-top: 10px;
}