Tutorial Retina Display Media Query

For including high-res graphics, but only for screens that can make use of them. "Retina" being "2x":
@media
(-webkit-min-device-pixel-ratio: 2),
(min-resolution: 192dpi) {
/* Retina-specific stuff here */
}
Or other highish-res:
/* 1.25 dpr */
@media
(-webkit-min-device-pixel-ratio: 1.25),
(min-resolution: 120dpi){
/* Retina-specific stuff here */
}

/* 1.3 dpr */
@