form , body.view {
    font-family:sans-serif;
    max-width:600px;
    margin:0 auto;
}

.message {
    padding:10px;
    border:1px solid black;
    font-size:14px;
    display:none;
}

.message.visible {
    display:block;
}

#message_ok {
    background:lightgreen; border-color:green;
}

#message_error {
    background:lightcoral; border-color:red;
}

textarea {
    width:100%;
    box-sizing:border-box;
    resize:vertical;
    height:200px;
}

button {
    display:block;
    margin-left:auto; margin-right:auto;
}

#content_zone {
    border:1px dotted gray;
    padding:10px;
}