Here are some resources I have put together to get you started on your web development path.
I recommend starting with Codecademy. Codecademy does a fantastic job of introducing you HTML, CSS, JavaScript and more
W3Schools is similar to Codecademy in many ways. There are free and paid courses, and an interactive environment you can play with code in the browser.
The Official Mozilla Web Docs from the Mozilla Developer Network (MDN)
Downloadable high quality documents from GoalKicker.
Check out the developers roadmap. A continuously updated guide showing the technologies involved to become a Full Stack Developer.