The best way to learn is through trial and error. The second best way is to learn from the people in the graphic design and web development fields.
Here are some graphic design, web dev, and user experience blogs that I follow.
This blog talks about CSS tutorials, experiments and tools. I subscribed to this email newsletter in January of 2018. I learned about how to use variable fonts, a CSS grid, and other DevTool extensions. It is a great CSS newsletter!
This email newsletter is a weekly digest of top-notch front-end news, articles, and tutorials. It includes HTML, CSS, browser tech, etc.
This is another great blog for CSS grids. This email newsletter has more news related to the web dev world, which I appreciate! The community is always growing and changing. I learned from other people's experiences. Such as, when someone tried to browse the web without CSS! It was a pure HTML page.
I just started following this UX blog. It has great HCI based illustrations in their newsletters to get you inspired. They accept that UX has a lot of clutter, and they want to try to straighten out the folds to make user experience design more understandable.
This blog helps backend developers stay on top of what is going on in the front-end spectrum.
This company has a pretty cool app. The blog itself talks about UX and design news.
Lynda.com is also a good learning platform. Find out if your local library offers a free membership with Lynda. Otherwise it is a paid membership.