I noticed today that the domain chemwiki.ucdavis.edu redirects to chem.libretexts.org. While most of the content is still available there, quite a few links may have gone rouge on our site.
The switch must have happened sometime in July last year.
If you find a broken link I suggest you check if there is a version archived at https://archive.org/web/ and fix the content. If you don't know what to do, you can of course flag for moderator attention.