body{
background-image:url(fondo.jpg);
background-repeat:no-repeat;
background-position:center center;
background-attachment:fixed;
-o-background-size: 100% 100%, auto;
-moz-background-size: 100% 100%, auto;
-webkit-background-size: 100% 100%, auto;
background-size: 100% 100%, auto;
}