Just yesterday I blocked the bots from my blog using this[1]. Of course whether these bots respect robots.txt nowadays is a different question altogether
I learned HTML and CSS mainly from MDN, so that's where I suggest you look. As for stuff I use in css most often I can only recommend a few articles and such. Learn how to use Flexbox and CSS Grid though for sure (as those are the two most modern ways to layout an HTML page) as well as CSS Positioning [0] (which is some of the older ways to lay things out).
For JS there are some online books that are gold mines the problem is finding them. One is Eloquent JavaScript which is available to read online for free here [1].
Though I've never actually finished the whole thing it does a pretty great job explaining JS to the uninitiated.
My other favorite books in JS are actually all from the same person Axel Rauschmayer. All of his books are available online for free here [2]. He has a really good way of explaining in my opinion and his books kind of take out all the fluff.
[1]: https://github.com/fardog/fardog.io/commit/b2e3eac838ea25209...