html,
body {
  height: 100%;
  width: 100%;
  position: relative;
}
html .bg,
body .bg {
  opacity: 0.3;
  height: 100%;
  width: 100%;
}
html .main,
body .main {
  overflow-y: auto;
  height: 100%;
  width: 100%;
  position: absolute;
  left: 0;
  top: 0;
}