In my Perl ＆ Python Tutorial, i have about 50 links to documentations at python.org. For example, about 15 URL have this form: 〔http://python.org/doc/tut/node7.html〕 and about another 15 has this form: 〔http://python.org/doc/lib/typesseq-strings.html〕. As of today, all these links are 404 errors. No redirect nor any measure to tell user how to find that file.
I truely hate sites that do not take consideration of URL permanence. This has also happened to FSF. See: A Record of Frustration in IT Industry; Disappearing FSF URLs.
Link maintenance many not be easy for sites with large number of files, such as documentation. But site owners should at least be considerate of this issue. It's not too difficult to maintain permanent links. There are many solutions, such as redirects (Apache server URL rewrite, html refresh tag, file aliases), or provide dynamically generated page that tell user where the info might went.
When you create new content, you should also plan ahead on possible URL changes. For example, if it is a documentation, you might include version number there, ⁖ 〔example.com/v1/doc.html〕,〔example.com/v2/doc.html〕, 〔example.com/latest/doc.html〕. This way, you can have permanent URL for almost all your URL without much management.
So, what does this mean to you?