Retina CSS example

gistfile1.css

@media only screen and (-moz-min-device-pixel-ratio: 1.5),
       only screen and (-webkit-min-device-pixel-ratio: 1.5),
       only screen and (min-device-pixel-ratio: 1.5)
{
  #test {
     background: url(../images/[email protected]) no-repeat center center;
     -webkit-background-size: 25px 25px;
     -moz-background-size: 25px 25px;
     background-size: 25px 25px;
  )
}