We do a lot of linking to Wikipedia. But Wikipedia pages are essentially volatile. How can we be sure that, when you follow a link from here to Wikipedia, the text that you see there will have any connection at all to the text that we saw there when we made the link?
In many cases, we don't simply link to the Wikipedia page, which would always give the current revision of it at the time you followed the link. What we link to instead is a particular revision of the page, which won't ever change. This is called a permalink. The URL of a permalink looks something like this:
http://en.wikipedia.org/w/index.php?title=List_of_guitar_tunings&oldid=263138490
As I write that actually takes you to the current revision of the page List of guitar tunings, but by the time you read this it may well be a past revision. The point is, it will always point to that particular revision, or to nothing. If the page is deleted, or even if that revision of the page is deleted but not the whole page (which is extremely rare but does happen, say for example where legal threats are involved) then the link will be broken. So what you read there is exactly what I read there, or nothing.
Not all links to Wikipedia are of this format, but probably many of them should be.
Yes, easily. You can permalink to almost any wiki. We're tempted to say, to any competently run wiki that's open to the public to read!
Or at least, think hard about whether that's really what you want to do. It may be.
TOEOT is in some ways more reliable than Wikipedia. It's a lot more controlled. There you can even edit most pages anonymously, but here you can't. You can comment on any page here just by creating a {free} pbwiki account, without any approval (and please do), but to edit the text of the page you first need to show some bona fides.
So if you want the best information on the subject, you probably want the current page here, regardless of what it is at the time. It's reasonable to think that any changes are improvements, and perhaps corrections.
On the other hand, if you're citing it, you may want a particular revision. It depends where and how you're citing it. At Wikipedia, for example, if you were citing this page in the text, using the ref tags for example, a permalink would be most appropriate. On the other hand, if you were listing it in a Further reading or External links section, a permalink would probably be wrong.
(Actually, despite what we said above, there's currently a bug in pbWiki that means you can't permalink to the current revision of the page. So if you want to do that, send us a message and we'll do a trivial update to the page so you can then permalink to the revision you want.) The links in these instructions will open in new windows, BTW, to make it easier to come back herre.