Except for Wikipedia articles, which are unlikely to disappear, I have tried to provide as many links as possible in the form of archived links via the Internet Archive. These links look like https://web.archive.org/web/timestamp/https://the.archived.website.com/some/archived/page. The advantage is that you can still access the resource without encountering a 404 error if the original site no longer exists or the page has been moved.
Note, however, that the Internet Archive is not perfect and does not save some images or comment sections. For example, in Reddit threads, only the main post is saved, not the discussion. It may therefore be useful to copy and paste only the part of the original URL https://the.archived.website.com/some/archived/page (and pray for the site in question to still exist).