I'd definitely start with codeacademy. There's two ways I look at it, if you want to be front end and start easy then go into html and javascript front end design then work to the back end. If you want to be a software developer or engineer start with back end development aka C, C# etc, but it will take more math. Up to your own path. I'd also suggest a small project idea in your head you want to accomplish. I just wanted to create a website, did it and then lost my passion, but in the process of that project learned a lot. Lastly, paying someone on upwork.com a dev for example to keep you accountable and teach you javascript for $5 an hour is actually a great hack for me after I finished codeacademy.
Definitely recommend Udacity! They offer various free courses and nanodegrees in topics like full stack, mobile, and react. I’ve taken a few of their nanodegrees and supplemented with other online courses from Wes Bos and React Training to good effect.
MDN has some great, up-to-date docs on the underlying techs of HTML, CSS, and JS.