转自：https://blog.csdn.net/qq_44938782/article/details/100530324

::-webkit-input-placeholder{/*Webkit browsers*/
color:#999;
font-size:16px;
}
:-moz-placeholder{/*Mozilla Firefox 4 to 8*/
color:#999;
font-size:16px;
}
::moz-placeholder{/*Mozilla Firefox 19+*/
color:#999;
font-size:16px;
}
:-ms-input-placeholder{/*Internet Explorer 10+*/
color:#999;
font-size:16px;
}