@media onlyscreenand (min-device-width:320px){
//针对iPhone3
}
@media onlyscreenand (min-device-width:320px)and (-webkit-min-device-pixel-ratio:2) {
//针对iPhone4,5c,5s, 所有iPhone6的放大模式，个别iPhone6的标准模式
}
@media onlyscreenand (min-device-width:375px)and (-webkit-min-device-pixel-ratio:2) {
//针对大多数iPhone6的标准模式
}
@media onlyscreenand (min-device-width:375px)and (-webkit-min-device-pixel-ratio:3) {
//针对所有iPhone6+的放大模式
}
@media onlyscreenand (min-device-width:412px) and (-webkit-min-device-pixel-ratio:3) {
//针对所有iPhone6+的标准模式,414px写为412px是由于三星Nexus6为412px，可一并处理
}
