> Dead posts aren't displayed by default, but you can see them all by turning on 'showdead' in your profile.

>If you see a [dead] post that shouldn't be dead, you can vouch for it. Click on its timestamp to go to its page, then click 'vouch' at the top. When enough users do this, the post is restored. There's a small karma threshold before vouch links appear.

[0] https://news.ycombinator.com/newsfaq.html