textarea [class = 'content'] :: - webkit-input-placeholder, css reason does not take effect

Be sure to write separately, will fail separated by commas

textarea[class='content']::-webkit-input-placeholder {
    color: #E1E1E1;
}

textarea[class='content']:-moz-placeholder {
    color: #E1E1E1;
}

textarea[class='content']::-moz-placeholder {
    color: #E1E1E1;
}

textarea[class='content']::-ms-input-placeholder {
    color: #E1E1E1;
}