html{
    background:url(../ima/preventivo.jpg) no-repeat fixed center;
    -webkit-background-size:cover;
    -moz-background-size:cover;
    -o-background-size:cover;
    background-size:cover;
}

body{
	margin:0;
	padding:0;
}

img{
	height:100%;
	width:100%;
}