Moderator Edit: The accuracy of w3schools.com has been challenged in another thread. In order to not pollute the original thread, the thread has been moved here.
Note to All: Please feel free to post about your experience in using w3schools.com, both good and bad.
Be a bit careful there though. That's just a commercial setup with a url which seems intended to give an impression of authority, or of connections with standards bodies, but actually has no status, and is often unreliable.
If you want something to rely on, the standards are at:
The KM Wiki article itself references the w3schools article on XPath. That is what I was referring to.
IAC, I have used w3schools for years on many differents topics of HTML, CSS, and JavaScript, and have always found them very reliable.
They are usually much easier to read and learn from than many other sources.
If you believe there is an error on any of their pages, I'd suggest you submit a bug report to them.