header {
    position: fixed;
    top: 0;
    width: 100%;
    height: auto;
    -webkit-backface-visibility: hidden;
    backface-visibility: hidden;
    z-index: 99;
    background: #ffffff;
    min-height: 100px;
    -webkit-transition: all 0.3s ease-in-out;
    -moz-transition: all 0.3s ease-in-out;
    transition: all 0.3s ease-in-out;
}