div.header {
    background-color: #ffffff;
    border-bottom: 3px solid #1c66ba;
    display: flex;
    width: 100%;
}

div.header > a > div {
    -webkit-flex: 1;  /* Safari 6.1+ */
    -ms-flex: 1;  /* IE 10 */
    flex: 1;
    padding: 15px 20px;
    color: #000000;
    -webkit-transition: all 0.32s; /* Safari */
    transition: all 0.3s;
}

div.header > a > div:hover {
    background-color: #1c66ba;
    color: #ffffff;
}

.active {
    background-color: #4CAF50;
}