A good place for documentation is MDN (Mozilla Developer Network)
https://developer.mozilla.org/en-US/docs/Web. They have extensive documentation with regards to web technologies. I suggest he read up about HTML first, getting the first few basic elements on the page. Then he can move on to CSS to style up the page.
At this point, you can practically build basic webpages with just HTML and CSS. From here, you can take 2 paths: A graphics designer or a front-end developer.
A graphics designer leans more to design rather than building apps. This requires a basic of jQuery, but mastery of Photoshop. A good place to learn is reading articles from Smashing Magazine http://www.smashingmagazine.com/
A front-end developer leans more to app-building rather than design. This requires knowledge of JavaScript libraries and best practices. For this, select your basic set of frameworks and master them. Suggestions range from jQuery, Bootstrap, to full-fledged frameworks like Ember and Angular.
