JSFiddle - React, Tailwind, and code Playground

HTML

<div class="loginform">
    <!--Inizio bordatura testo arrotondato-->
    <form action='normativa.php' method="POST">Username:
        <input type="text" name="username" maxlength="30" size="32" />
        <br>
        <br>Password:
        <input type="password" name="password" maxlength="12" size="14" />
        <input type="submit" name="log" style='padding:10px' value="Login" />
        <input type="button" onClick="window.location.href='logout.php';" style='padding:10px' value="Logout" />
    </form>
</div>
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum imperdiet, mi in ultricies condimentum, mauris risus lacinia nibh, vitae suscipit sem risus sit amet ante. Duis lacus odio, eleifend id sollicitudin et, lobortis a nisi. Vestibulum tortor nulla, tincidunt eget commodo quis, mollis tempor purus. Donec ut lectus ipsum, et eleifend nisi. Phasellus rhoncus justo sit amet magna rhoncus dignissim. Nullam at ultrices nunc. Suspendisse eget ante orci, at vestibulum urna. Cras in massa eu felis viverra volutpat nec sit amet orci. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac</p>

CSS

body { width:600px;  font-family:Comic Sans MS; color: white; }
.loginform {
    color: yellow;
    /*giallo*/
    padding: 3px;
    border: 20px solid;
    border-width:2px;
    border-style:inset;
    /*  margin: auto;*/
    margin-bottom:10px;
    /* Da la distanza dal bordo della barra degli indirizzi*/
    border-radius: 10px 10px 10px 10px;
    -moz-border-radius: 10px 10px 10px 10px;
    -webkit-border-radius: 10px 10px 10px 10px;
    box-shadow: 4px 8px 10px #a6aeb7;
    text-align:center;
}
.centra {
    margin:auto;
    /*e altre caratteristiche*/
}
.center {
    margin-left:auto;
    margin-right:auto;
    width:100%;
    background-color:#b0e0e6;
}
body {
    background-color: #000000;
}
.messaggio {
    /*poi metti i valori che vuoi*/
    /*background-color:#666666;*/
    /*background-color:#FFFFDE;*/
    background-color:#000000;
    border-width:2px;
    border-style:inset;
    margin:auto;
    border-radius: 10px 10px 10px 10px;
    -moz-border-radius: 10px 10px 10px 10px;
    -webkit-border-radius: 10px 10px 10px 10px;
    box-shadow: 4px 8px 10px #a6aeb7;
    text-align:center;
}
.centra {
    margin:auto;
    /*e altre caratteristiche*/
}
.bordato {
    border:2px solid #000000;
    border-radius: 80px 80px 80px 80px;
    -moz-border-radius: 80px 80px 80px 80px;
    -webkit-border-radius: 80px 80px 80px 80px;
}