gistfile1.css

a.email-share {
  display: block;
  height: 34px;
  width: 34px;
  background: url(../images/btn_mail.png) no-repeat #302f2f;
  text-indent: -9999px;
}

@media all and (-webkit-min-device-pixel-ratio: 2),
  all and (min-device-width: 641px) {
    
  a.email-share {
    background: url(../images/[email protected]) no-repeat #302f2f;
    background-size: 34px 34px;
  }

}