This looks like a great resource for anyone setting out to learn how to make websites.
Link archive: December 7th, 2015
The A-Z of HTML, with an example for each and every element. Comprehensive and impressive.
A subset of one of my favourite sites on the web:
Explore the Arctic of the past from the deck of a whaling ship.
Choose your vessel and get transcribing.
A list of known bugs (and workarounds) in flexbox implementations. This is going to be handy to refer back to.