.fixed-background{
    background:url(../img/background1.jpg);
    position:absolute;
    background-size: cover;
    top:0;
    bottom:0;
    right:0;
    left:0;
   z-index:-2;
}
.fix-background{
    background:url(../img/background2.jpg);
    position:absolute;
    background-size: cover;
    top:0;
    bottom:0;
    right:0;
    left:0;
   z-index:-2;
}