Shows stories which have hit the front page ever, in the order of their posting. If it's currently on the front page, the link is orange. If it's not, it's black. It's very interesting to watch how frequently highly upvoted and commented posts turn black, while their temporal peers remain.
Anecdotally, there appears to be trend of positive/neutral news about YC companies remaining on the front page the longest, the latest shiny technology sticks around for awhile longer than average, and pretty much any negative news disappears almost instantly.
For example, as of this instant in time, there is an article about Angular2 which remains on the front page while more highly upvoted and commented articles about laptop security, AT&T discrimination, and a Nintendo Switch CVE discussion are all gone from the front page.