or better yet, just make it so that HN's pagination links don't expire.
1. Go to page 1
2. Read a couple of articles on page 1
3. Hit next page and receive error.
4. Go back to page 1
5. Go to page 2
6. Read a couple of articles from page 2
7. Go to next page and receive error.
8. Go to page 1
9. Go to next page
10. Go to next page
11. Read article from page 3
...
I would be curious to know what percentage of requests to HN return "Unknown or expired link". If I were in control of this website, I would consider this behavior to be unacceptable.
Say I take too long entering a comment, I get distracted at work, then hit submit. I'm taken to the homepage. Did the comment go though nor not? How an I supposed to know what the hell happened?
I agree 404 etc pages /should/ be better designed to inform the user then give them links/options to carry on their journey.
Here: http://www.bbc.co.uk/cbbc/404.shtml - we tried to explain a little about the problem, to a young audience and then offer them two ways of continuing their journey - go to homepage or use search.
We also made other URLs fail gracefully. If a user was at: http://www.bbc.co.uk/cbbc/thingstodo/by/type/printgames and then 'hacked' the URL to get http://www.bbc.co.uk/cbbc/thingstodo/by/type - we still offered them a page that correctly renders and has the information they were looking for - though we'd never link to this page ourselves (the correct root here would be http://www.bbc.co.uk/cbbc/thingstodo )
So it seems like there's some real UX concerns expressed below re: auto redirect to homepage w/o sufficient error messaging. One solution would be to render the error message on the top of the homepage "Sorry, articles expired like milk so we brought you back to the homepage for fresh articles.".
I would actually prefer an infinite list of stories with stories moving up and down in a clean AJAX'ed way based on live votes so at any given time you are seeing the most up to date list of articles.