Mozilla Developer Network or MDN is a development documentation website for web standards. In these couple of weeks, I learned how to use the MDN to check whether I use my HTML correctly.
The MDN has a lot of information, which, together with the W3C and WHATWG, can not only give you a hint on how to use your tags, but also why you should use them this way.
Overall it was a nice couple of weeks and I hope to learn some new stuff next!