header {
background: url(image.jpg);
}
@media (min-resolution: 192dpi){
header {
/*using the larger image for retina screens*/
background: url(image@2x.jpg);
}
}
For Safari:
@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
header {
background: url(image@2x.jpg);
}
}
/*
In every HTML element everything EXCEPT THE MARGIN is considered the background layer and is transparent by default.
*/