The articles you speak of, at least that I think you're speaking of, would fall into the printed category. An electronic form of a publication isn't exactly the defining factor, but that the publication, despite being online, is published an official journal that is peer reviewed.
Something like this,
www.publish.csiro.au/paper/ZO9940001.htm
, which is technically a website, shouldn't be cited as webpage, but should be cited as "Geiser, F (1994). Hibernation and Daily Torpor in Marsupials - a Review. Australian Journal of Zoology 42, 1–16." It's from a real life publication and that is what distinguishes it in quality and verifiability from internet only sources.
The idea that I'm trying to convey, and if anyone disagrees on this please discuss it, is that information obtained from peer reviewed journals and books are a better quality than Joe Bob's Glider Website. Peer review is the most important thing in science, as it allows kooky ideas to be weeded out.
These are only guidelines and shouldn't be considered as strict rules. Some topics simply may not have published documentation, so internet only sources would be inevitable. Perhaps a better way to think of this is not as guidelines, but as goals for a topic or article to try to achieve through collaboration.