.ad {
  position: fixed;
  border: none;
  z-index: 0;
}

.ad.top {
  top: 0;
  left: 0;
  width: 100%;
  height: 80px;
}

.ad.bottom {
  bottom: 0;
  left: 0;
  width: 100%;
  height: 80px;
}

.ad.left {
  top: 0;
  left: 0;
  width: 120px;
  height: 100%;
}

.ad.right {
  top: 0;
  right: 0;
  width: 120px;
  height: 100%;
}