- Is there some official announcement explaining what happened to the site and whether it is definitively discontinued?
- Do you happen to know whether the links to this site might start working again in the future?
Are there reasonable ways to fix such links?
- If the OP included enough information about the paper in the post, it probably doesn't matter whether the link no longer works - knowing at least the author and the title is enough to locate the article.
- In some cases the link might have been archived in the Wayback Machine. But we will not always be that lucky.
- The links contain some kind of identifier - but it is unclear how to get further data from that identifier. (See also this question on Academia: How does CiteSeerX's DOI parameter work?.)
I tried to check whether there are some posts where Wayback Machine links have already been added for those links.
Search returns 22 posts with URLs containing
*web.archive.org*citeseer* networkwide. (None on this site, 3 on MathOverflow.)
Looking specifically at the link from this MathOverflow post, we can see that the Wayback Machine link uses the id 10.1.1.43.3848. The same paper can be now found under pid/c4d9cd7ba35b6d295fe19025eafe4561fe19d75e. So this instance would suggest that CiteSeerX changed the identifiers they're using.
While this could be seen as a networkwide issue, I posted here. One reason is that I do care more about the posts on this site rather than elsewhere. The other things that efforts to fix dead links seem to be rather active on this site. Of course, if more experienced people suggest that Meta Stack Exchange would be a better place for this, I will post there.