Learn HTML(5) and CSS
W3Schools is the largest web developers site on the Internet with HTML(5) and CSS web development tutorials and references covering most aspects of web programming.
Easy to Use Tutorials
W3Schools focuses on simplicity, practicing easy and straight-forward learning by using simple code explanations, and illustrations on how to use it.  Tutorials start from basic level, and move all the way up to complete professional references.
Online Editor
W3schools presents thousands of code examples.  The site contains an online editor allowing teachers/students to edit examples and execute computer code experimentally, to see what works and what does not, before implementing it.

W3Schools is a completely free developers resource.  Permission is granted to link the site and use small snippets of code in examples.