> Why can't the "More" link just link to news.ycombinator.com/news?page=2 which gives me number #31-60 of the top trending links?
1. HN deals with your interaction by assigning a session index to your initial contact.
2. This index allows HN to keep track of which page of which section you're visiting, so if you click "More" the HN sever knows what do to -- it has a stored context for your request.
3. The HN server has limited resources, so if an index goes unused for more than a few minutes, the server reclaims the index for reuse.
4. If you wait too long before making a server request like clicking "More", it's possible that your index will have been reclaimed and assigned to another user. If this happens, you see the "expired link" message.
5. After your index has expired and been reclaimed, the HN server has no way to interpret your command to proceed -- proceed to where?
6. Also, if you wait long enough, the front page (and all subsidiary pages) will have changed contents, so the pages you're viewing are no longer current, consequently the server can't deliver "page 2" for the simple reason that that version of the page no longer exists.