SoloLearn is a “learn by doing” and “social learning” platform.
It offers courses and tutorials especially about coding and web development.
The courses are self-paced and made up of texts and videos taken from many different sources.
SoloLearn courses are very useful if you are looking for a quick overview about a markup or programming language that you have never used before.
Have a look at the certificates that I have earned at SoloLearn.