JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
    <link type="text/css" rel="stylesheet" href="styles.css"/>
</head>
<body>
    <div id="cabecera" class="relleno">
        cabecera
    </div>
    <div id="menu" class="relleno">
        menu
    </div>
    <div id="botones" class="relleno">
        <input type="submit" value="Guardar"/>
        <input type="submit" value="Eliminar"/>
    </div>
    <div id="contenido" class="relleno">
        contenido
    </div>
</body>
</html>

CSS

#cabecera{
    height: 80px; 
}

#menu{
    float: left;
    height: 80px;
    width: 180px;
    margin: 8px 8px 0 0;
}
 
#botones{
    overflow:hidden;
    margin: 8px 0 0 0;
    
}

#contenido{
    height: 80px;
    overflow:hidden;
    margin: 8px 0 0 0;
}

body{
    margin: 8px;
}

.relleno{
    background: #f0f0f0;
    border: 1px solid #aaa;
    padding: 5px;
}