Which should you learn first? HTML, CSS or JavaScript? None.

By none, I mean...

...learn them at the same time, not one after another.

To accomplish this, it helps to have small challenges, like this one:

Re-create this MacOS calendar app icon

Steps you could follow

1. How might you mark-up a month and date?
2. How might you style your new page elements, even at a basic level: fonts, colors, size, background colors, and page centering?
3. How might you dynamically generate the month and date?
4. How might you optimize your CSS, refactor your JavaScript, and account for accessibility by using more semantic HTML elements?

If you feel stuck, use this game I made to learn all three languages each day, increasing your difficulty as you grow your skills:

Fix a function!