https://developer.mozilla.org/en-US/Learn is a good place to start.

http://eloquentjavascript.net/ does a great job, especially in the later chapters.

http://learn.shayhowe.com/advanced-html-css/responsive-web-d... 'Responsive' site design is a must-have now-a-days.

http://alistapart.com/article/dao The philosophy and theory of web design

I have some other links you may be interested in on a blog post I wrote a while back: http://mygen.ca/develop-developing-developers/