CSS:
Style Placeholder-Attribute

::-webkit-input-placeholder { /* Chrome/Safari/... */
    font-size: 0.8rem;
    color: grey;
}

:-moz-placeholder { /* Firefox 18- */
    font-size: 0.8rem;
    color: grey;
}

::-moz-placeholder {  /* Firefox 19+ */
    font-size: 0.8rem;
    color: grey;
}

:-ms-input-placeholder {  /* IE */
    font-size: 0.8rem;
    color: grey;
}