Does an (old) answer that contains only a dead link deserve a downvote?
If the answer contained so little information without the link, it wasn't a good answer to begin with and probably deserved a downvote at the time. Now, since the link is broken (unless you can fix it, in which case please do!) it should be downvoted as it's now even more useless.
The downvote tooltip says "this answer is not useful". It doesn't say "this answer was not a fair attempt at an answer". Vote for what the post is, not what it was trying to be.
My typical thought process is:
- If the answer provides some context, but not much, and most of it is in a relatively obscure link: leave a comment about the broken link, possibly downvote depending on if the answer is otherwise well-formatted/good/etc.
- If the answer contains a link that is easily findable (or known to have moved due to version updates): edit the link to point to a valid place if I have time. Otherwise I comment and possibly downvote (typically just a comment, though).
- If the answer contains no context and only a link which cannot be updated reasonably, I flag as "Not an Answer". Even before the 404 it is arguably not an answer; after the link breaks it most certainly is not an answer, to me.