This is probably not very important, but when I see Google Books link, I tend to edit them from other variations (books.google.fr, books.google,it, etc.) to books.google.com. I assume that in most cases the user did not intend to post a link specifically for their language variation - but that's what they happend to copy-paste. mathoverflow.net/review/suggested-edits/164751
Of course, I would not be surprised to see books.google.sk in some of my posts. But I try to avoid doing that - at least when I notice this.
@Martin I went through all the links in this search, and it seems only those ones are broken that begin with arxiv4. Those that look like arxiv-web3, as in your example, seem to redirect correctly. A global search shows that there are 9 such broken links, all of them on MathOverflow.