Lots of inaccurate information. This low-quality resource does more harm than good.
A good explanation here : http://w3fools.com/
Better educational alternatives here : http://w3fools.com/#what-should-be-done
This website is very useful, but it's misleading and even a little scammy. It leads you to believe that it's affiliated with W3C, but it isn't. They have more information about W3C (next to the w3schools logo!) than about who writes their own content, and never explicitly state that they are not affiliated. The value of their "certifications" is dubious.
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