.main-panel {
    width: 70%;
    height: 70%;
    margin: 30% auto;
    position: relative;
}

.main-panel table {
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
}

#panel1 {
    display: block;
}

#panel2 {
    display: none;
}