When I visit
Replies column I can see how many new posts have been added. Drupal also marks them with a
I'm wondering how does drupal determine which replies are new for me? Are they new since my last visit to the page, or my last logout from drupal.org? In case the later is correct, how does drupal know when I loggeout out last time?
I'm very interested to know what algorithm is behind this nice feature?