It has its uses, but W3Schools has been criticized for being inaccurate[1], and there's better documentation out there now (HTMLDog and Mozilla Developer Center have been mentioned[2][3]).

[1] http://w3fools.com/ [2] http://htmldog.com [3] https://developer.mozilla.org/en-US/

If by "good overview" you mean "often incorrect and sometimes extremely harmful" you are correct:

http://w3fools.com/