To target only webkit, which includes Google and Safari, encompass all the CSS that you want to use just to target Webkit in the following @media block:
@media screen and (-webkit-min-device-pixel-ratio:0) {
.myClass { background-color: #FF0000; }
#myId {color: #0000FF;}
p, a, li {text-shadow: 3px 3px 3px rgba(0, 0, 0, 0.4);}
}
