Dana Sallow wrote me a note:

“Hello – I read your page markohoven.com/2020/05/15/css-stylesheet-selectors/ and have two words: incredibly useful! I loved the HTML-related resources you mention there. I shared your post with a co-worker, and he shared with me a very helpful guide on how to use HTML. https://www.websiteplanet.com/blog/html-guide-beginners/ Since your readers might need this for either their work or personal life, I do believe they’ll find it useful if you add it to your page. Thanks again for the resource! Best, Dana.”
So here it is: