body,html {
  height: 100%;
  margin: 0;
}

.bg {
  /* The image used */
  background-image: url('nanobk.jpg');

  /* Full height */
  height: 100%; 

  /* Center and scale the image nicely */
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;
}
.center {
  display: block;
  margin-left: auto;
  margin-right: auto;
  width: 50%;
}
a:link {
  text-decoration: none;
}

div.a{ 

  text-align: center;

}

.footer {
   position: fixed;
   left: 0;
   bottom: 0;
   width: 100%;
   color: black;
   text-align: center;
   font-size: 2vw;
}