· 对于只需要适配手机设备，使用px即可
· 对于需要适配各种移动设备，使用rem，例如只需要适配iPhone和iPad等分辨率差别比较挺大的设备
rem配置参考：
html {font-size:10px}
@media screen and (min-width:480px) and (max-width:639px) {
html {
font-size: 15px
}
}
@media screen and (min-width:640px) and (max-width:719px) {
html {
font-size: 20px
}
}
@media screen and (min-width:720px) and (max-width:749px) {
html {
font-size: 22.5px
}
}
@media screen and (min-width:750px) and (max-width:799px) {
html {
font-size: 23.5px
}
}
@media screen and (min-width:800px) and (max-width:959px) {
html {
font-size: 25px
}
}
@media screen and (min-width:960px) and (max-width:1079px) {
html {
font-size: 30px
}
}
@media screen and (min-width:1080px) {
html {
font-size: 32px
}
}