#header {
  position: relative;
}

#menu {
  position: absolute;
  right: auto;
  left: 0;
  bottom: 0;
  top: 0;
}

#tab {
    position: absolute;
    overflow: auto;;
    right: 0;
    bottom: 0;
    top: 0;
    z-index: 10;
    width: 70%
}