From time to time, answers can be posted to the site which, at the time are valid but later become invalid without any fault of the original answerer. For example, a number of answers to this challenge use domains such as http://ppcg.lol and http://ppcg.ga, which, at the time, worked, but have since expired and so the answers are technically invalid.
Typically, I would advocate for always deleting invalid answers. However, in this specific case, I'm not entirely sure that deletion is the correct approach:
For the linked challenge specifically, a total of 4 out of the 50 answers do not use a broken URL, meaning that 46 answers would either need to be updated (unlikely, given the question is almost 7 years old) or deleted. Such mass deletion of answers would be incredibly disruptive to the challenge.
In general, the reason that answers like this are invalid are not any fault of the original answerers. Rather, it's because of external factors out of their control that invalidate their answers, such as domains expiring or even languages being updated.
In this case, we would effectively be requiring answers to keep up to date over multiple years, or else be marked invalid by something out of the answerers' control.
These are simply my personal opinions on the matter though, and feel free to share your suggestions as well. What does the community believe is the appropriate course of action here?
In fact, this issue appears to be not uncommon, especially for internet challenges. For example,
- All answers here are invalid, as https://strawpoll.me/ is closing down
- Answers here are susceptible at any time to being invalidated by another answer being posted with the same search text/by the same user