<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>Forms</title>
  <style>
    input:optional {
      border: 2px solid #009999;
    }
    input:required {
      border: 2px solid #000099;
    }
  </style>
</head>
<body>
  <section>
    <form name="myform" method="get" action="process.php">
      <p><input type="text" name="myname"></p>
      <p><input type="text" name="mylastname" required></p>
      <p><input type="submit" value="Send"></p>
    </form>
  </section>
</body>
</html>