title: Custom Div when press browser back button
body: <p><a href="https://i.stack.imgur.com/Q5uHx.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Q5uHx.png" alt="enter image description here"></a></p>
  
  <p>Pressing Back button in Google Plus will show this nice Div, instead of the ugly alert box, how is this achievable? Notice the URL has not change when press 'Back'.</p>
  
  <p>Thanks.</p>
  
  <p>Edit:
  I should be more specific in my question. I am not interested at how sexy the pop-up modal, but I am looking for method or API to hijack the back button behavior. </p>