You can archive it through various services and save an exact screenshot/html snippet/text that can be cited. In the sources you add "Retrieved on.." and "Archived link... Secondary archived link.." .. and some journals are allowing artifacts these days too. Typically this is used for code or data sets, but it could also be used for copies of the anonymous source material.

You should be able to follow the references in a paper even in a hundred years or later. This obviously works quite well for print. Blogs, wikis and other websites are in general not permanent enough to be useful as references. Even when you archive them, the archive is likely to disappear much earlier than the paper for which it was made.

In fact, I fear that the trend to publish supplemental material may lead to another crisis because a lot of that material is not managed and archived well and may disappear without warning. Some papers contain important details like long, involved and non-obvious calculations only in their supplements and are not really reproducible without them.