JSFiddle - React, Tailwind, and code Playground

HTML

<div id=container>            <div id=wrapper>
    <form method=post action='load.php'>
        <fieldset>
            <legend>Register</legend>
                <input type=text name=name placeholder='Your Name' title='Username' autofocus required />
                <br>
                <input type=text name=mail placeholder='Email' title='Email' required />
                <br>
                <input type=password name=password placeholder='Password' title='Password' required />
                <br>
                <input type=submit name=submit value='Sign up' />
        </fieldset>
    </form>
</div></div>

CSS

#container {
    clear:both;
    -webkit-flex:1 0 auto;
    -ms-flex:1 0 auto;
    flex:1 0 auto;
}
#wrapper {
    max-width: 18%;
    min-width: 11em;
    padding: 1.5em 0;
    margin: 0 auto;
}
fieldset {
    padding: 0.6em;
    border: 0.08em solid #666;
    box-shadow: 0 0 0.09em #666;
}
legend {
    float: left;
    margin-top: -1.5em;
    background: #FFF;
}