css3@media 兼容ios4，ios5，ios6,6plus

//device-height  设备可视高度
//-webkit-min-device-pixel-ratio    是设备上物理像素和设备独立像素,设备像素比率

@media (device-height:480px) and (-webkit-min-device-pixel-ratio:2) {
/* 兼容iphone4/4s */
html{}
}
@media (max-device-width:621px) and (-webkit-min-device-pixel-ratio:3) {
/* 兼容iphone6p */
html{}
}
@media (device-height:667px) and (-webkit-min-device-pixel-ratio:2) {
/* 兼容iphone6 */
html{}
}

/*魅族*/
@media only screen and (min-device-width :1080px) and (-webkit-min-device-pixel-ratio : 2.5){ }

/*mate7*/
@media only screen and (min-device-width :1080px) and (-webkit-min-device-pixel-ratio : 3){ }