Safari 6 and Chrome 21 added vendor-prefixed support for the proposed CSS4 image-set specification. This proposed specification is designed to support displays with different pixel densities (read: retina displays).
background-image: url(image.jpg); background-image: -webkit-image-set(url(image.jpg) 1x, url(firstname.lastname@example.org) 2x); /* Also include other prefixed versions of this ... */ background-image: image-set(url(image.jpg) 1x, url(email@example.com) 2x);
Safari 6 and Chrome 21 add image-set to support retina images →
Related: High DPI images for variable pixel densities →