Introducing forms to web apps

A form in a web application consists of a form HTML element that contains some input elements for entering data, and a button element for handling that data. The form can retrieve data and either save it locally or send it to a server for further manipulation. The following is a simple form that is used to log a user into a web application:

<form>
  <div>>>
    <input type="text" name="username" placeholder="Username">
  </div>
  <div>
    <input type="password" name="password"     placeholder="Password">
  </div>
  <button type="submit">Login</button>
</form>

This form has two input elements: one for entering the username and another one for entering the password. The type...