Ensure you have javascript enabled on your browser.
You will see an infinite number of prompt boxes right away. You can stop the test by typing 'stop' into the input line of the prompt box.
You can't prevent them even when you check the box to prevent more message boxes from showing.
I could have easily made an infinite number show and prevent you from leaving this page, forcing you to restart your browser.
Or worse, I could have kept prompting you for a password to your e-mail account and force you to stay on this page until you do.
