HTML5 Form Validation Without JS

HTML

<h2>HTML5 Form Valination without JS</h2>
<br/>
E-Mail: <input type="email" required /> <br/>
<br/>
Comment: <input type="text" />

CSS

input:required {
    background-color: rgba(255,0,0,0.2);
}

input:focus:invalid { 
    box-shadow: 0 0 1em red;
    border-color: red;
}

input:focus:valid { 
    box-shadow: 0 0 1em green;
    border-color: green;
}

body { font: 1em "Helvetica", sans-serif; }
h2 {   font-size: 120%; }