To get a basic understanding of HTML, CSS, and JS, you can find YouTube tutorials on how to create beautifully dynamic websites. If you want to go above and beyond the bare bones features of a functional UI, then you should look up YouTube channels that deal with the specifics of web design from creating floating menus to uploading animated backgrounds. One good YouTuber to watch is the TechGuyWeb, who runs Traversy Media. He uploads HTML and CSS crash courses for people who know nothing about coding at all. They can be over an hour long but everything is explained clearly and is easy to follow for beginners.
If you want to watch videos about front-end development, try following Jesse Showalter and DevTips, though the latter is now run by DataDavid. One other channel to recommend is The Coding Train as this guy makes coding fun by injecting some personality into his live streams on TensorFlow.js and game creation. Although those of you who are pros should probably look up the advanced CSS and SCSS course by Jonas to learn some shortcuts on compiling the code. One guy even started his own channel on making dribble shots in Webflow. The rest are more obscure channels that release videos on building a website from scratch. Case in point, many YouTubers like TechSquidTV, Coding Phase, and DreadedDev upload solo projects. For more information click here https://www.reddit.com/r/web_design/comments/8p9dmm/favorite_youtube_channels_where_you_can_watch/.