media selected css with sprite bg url

main.css

@media screen and (min-width: 1020px) {
  #content:before {
    content: " ";
    background: url("/assets/images/layout/content-shadow@2x.png") 0 -542px no-repeat, url("/assets/images/layout/content-shadow@2x.png") right 0 no-repeat;
    position: absolute;
    top: 0;
    left: -23px;
    right: -23px;
    display: block;
    height: 540px;
    z-index: -1;
  }
}