What are the post time visibility rules?

I often see that posts only a couple of hours old have vanished from the Latest Threads section. Is this only for posts that I have already seen, or is it true for any person making a random time entry?

Thanks, Don

The latest threads section is designed to list posts that are new since your last log-in, once you have logged in after a time window it classes these threads as noticed and will no longer display them in Latest Threads. If you require the list, you must go to Search and specify all threads in the last 24 hours (or whatever your time period need is).