I've looked at doing coursera but I'm struggling with some mental health issues right now and haven't gotten the gumption to get around to it. . . .
Codecademy is um. . . well it's a website that basically walks you through coding, but it's hard to explain? I find that it doesn't give you a lot of the "why" or "how" that you would get from a structured course like Coursera, BUT it's much more intuitive. Sort of like, you go through this website program that tells you what to do, you copy the code examples without understanding it so much and then you see what it does after you put it in. You learn about the "why" and the "how" as you go along learning the coding language.
Sort of like, when we're children, we learn how to make things plural by adding s. We know this because we copy the people around us. So, sometimes kids say mooses or deers instead of the correct plurals. Because they're learning by copying, they're applying rules across the board. It takes a while for them to pick up on the subtleties of the language. Codecademy teaches you code similarly to the way you learn your original language. You start by copying simple ideas, then you make mistakes, then eventually you start to learn the whys. Like why we don't say mooses.

It's not for everybody, but I'm a big fan.
But anyway, they do HTML, Python, CSS, and some others. It's a pretty awesome website to play around with. Though, I'll have to check out Coursera, last time I looked they didn't have specializations.