<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<form action="/pagina-processa-dados-do-form" method="post">
<div>
<label for="name">Nome:</label>
<input type="text" id="name" />
</div>
<div>
<label for="mail">E-mail:</label>
<input type="email" id="mail" />
</div>
<div>
<label for="msg">Mensagem:</label>
<textarea id="msg"></textarea>
</div>
<div class="button">
<button type="submit">Enviar sua mensagem</button>
</div>
</form>
