input 框设置placeholder文字的颜色

input::-webkit-input-placeholder{
    color:#999999;
}
input::-moz-placeholder{   /* Mozilla Firefox 19+ */
    color:#999999;
}
input:-moz-placeholder{    /* Mozilla Firefox 4 to 18 */
    color:#999999;
}
input:-ms-input-placeholder{  /* Internet Explorer 10-11 */
    color:#999999;
}