background: #ffff url(image) no-repeat top left is actually short for
background-color: #fff;
background-image: url(image);
background-repeat: no-repeat;
background-position: top left;
Setting the background-size property to cover makes background-repeat obsolete.
If you set background-image: url("../img/bg.jpg"), it makes no-repeat obsolete. The fixed does actually nothing there.
As Zuber suggested, just write the long hand properties.
body {
background-image: url("../img/bg.jpg");
background-attachment: fixed;
background-size: cover;
}
solved background-image in css not working properly [closed]