HTML <input> placeholder 属性

css

::-webkit-input-placeholder { /* WebKit, Blink, Edge */
    color:    #909;
}
:-moz-placeholder { /* Mozilla Firefox 4 to 18 */
   color:    #909;
   opacity:  1;
}
::-moz-placeholder { /* Mozilla Firefox 19+ */
   color:    #909;
   opacity:  1;
}
:-ms-input-placeholder { /* Internet Explorer 10-11 */
   color:    #909;
}

HTML input placeholder支持的属性

1. font properties
2. color
3. background properties
4. word-spacing
5. letter-spacing
6. text-decoration
7. vertical-align
8. text-transform
9. line-height
10. text-indent
11. opacity

来源：https://www.cnblogs.com/qiqi715/p/11493078.html