First of all, we have a little demo that illustrates the fact that, under certain circumstances, your browser's STS state can divulge whether or not you've visited a site. To try this, follow the link below, then click "Push my button" or reload the page. You will need to clear your history (or maybe site setting on later versions of firefox) to reset this demo.
Next up, we have something to demonstrate an STS 'cookie' - this uses the same principle as the above demo, but performs the trick over a number of subdomains to store data. Pick a number, enter it below and click 'Set the secret number'. Clear your cookies, reload the page if you like, then click 'Check the secret number' - you'll see the secret number you chose.