<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
</head>
<body>
<form class="box" action="index.html" method="POST">
<h1>Логин</h1>
<input type="submit" name="submit" value="Отправить" /><input />
</form>
</body>
</html>
<input type="submit" name="submit" value="Отправить" /><input />
</input>
<input type="submit" name="submit" value="Отправить">
<button type="submit" name="submit">Отправить</button>