Learning to append MDN to all my searches helped me out a lot. MDN is just a much better resource. And before I caught on I did assume a certain credibility and relationship between W3schools and W3C.
If you use Google, you can add w3schools.com to your list of sites blocked in search results. I did this and it makes MDN my top result almost 100% of the time when searching for spec-related information.
link: http://www.google.com/reviews/t screenshot: http://cl.ly/image/2l2r3f3y1a3x