.blanka {  background-attachment: fixed; background-image: url(back1.jpg); background-repeat: no-repeat; background-position: left top}
.blanka1 {  background-attachment: fixed; background-image: url(back.jpg); background-repeat: no-repeat; background-position: left top}
.blanka3 {  background-attachment: fixed; background-image: url(back2.jpg); background-repeat: no-repeat; background-position: left top}