A very interesting resource I came across last night,
We hope we can illuminate why W3Schools is a troublesome resource, why their faulty information is a detriment to the web, and what you (and they) can do about it.
To filter out w3schools from your searches, add -w3schools. Meanwhile, to get results from the Mozilla Docs Center, just prepend mdc.
Google might even take notice of behavior like that and demote these sites in the rankings.