body { 
  background: no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}
.logo {
     height: 100px;
     text-align: center;
 }

.logo img {
    height: 100px;
}

.header {
    margin: 30px 0;
}