.bg
{
  width: 100%;
  z-index: 0;
}
body {
  background: url('https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRvM_eaGaTy7cOQg_9Ca8w2BVTPOm5KLJq-SA&s');
  background-size: cover;
  background-position: center;
  background-attachment: fixed;
}