Moreover, the site in question, at its very top, suggests some very clear improvements to W3Schools, the most obvious and effective being to convert it into a wiki that will allow for self-correction and keeping the content up-to-date.
They also detail how there have been numerous attempts at building alternatives, but W3Schools retains too much unwarranted Google juice for those alternatives to be viable.
The people behind this project are also developers and contributors to projects like jQuery, Dojo, Prototype, Chrome Developer Tools, jQuery UI, svgweb, HTML5 Boilerplate...
W3C did not invent the term world wide web, www, or w3 - there is no deception.
I originally learned HTML and CSS from the W3 specs, but when I needed a quick reference page W3Schools were usually on the top of the Google search results. I usually spent about ten seconds clicking the link, reading the page, then leaving with the info I needed. Sure, I knew what W3C stood for, vs just plain W3, but I never even thought about the name.
I actually feel pretty bad now: I recommended W3Schools as a beginner PHP tutorial for a non-coding friend, after a StackOverflow thread recommended it. I just used the PHP manual myself, but she was after something friendlier. Don't suppose anyone knows a decent alternative beginners' tutorial which promotes modern PHP practices and will steer her away from shooting herself in the foot?
W3C was founded by (and remains directed by) Tim Berners-Lee, who did, in fact, invent both the term "world wide web" and the actual world wide web.
So to attack something that is on the whole good, which may be 99% accurate but not 100% accurate, seems mean-spirited. Someone put a lot of time into this, and it's a shame they didn't do something productive instead of destructive.