learning how to code
w3schools that's a classic one! this website teaches you everything you need to know about html, css, javascripts and many more.
html in 100 seconds a youtube video that quickly explains what html is and how it works in 100 seconds.
css in 100 seconds a youtube video that quickly explains what css is and how it works in 100 seconds.
beginning html5 and css3 for dummies if you wanna learn things like the old days of reading those "for dummies" books before looking at tutorials on the internet.
computer programming - javascript and the web khan academy teaches javascript, html, css, how to make a website and computer programming.
coding is easy, actually a youtube video that explains how easy learning how to code can be from a channel named easy, actually. along with a website he recommends, roadmap.sh
beginner frontend roadmap an easy roadmap if you want to begin making websites and frontend development from roadmap.sh
advanced frontend roadmap a detailed roadmap if you want to take some extra steps with making websites and frontend development from roadmap.sh
sadgrl's webmaster guide sadgrl has some guides on html, css and snippets.
petrapixel coding petra pixel has some guides and tutorials on how to make a website, how to use github, etc. and she also has a self-study checklist to check all the codes you know.

helpful stuff and tools for your site
codepen an online code editor and also a community of people sharing their code snippets. if you're looking for something like layouts, galleries, lightboxes, custom cursors and suchlike, you can find a code snippet shared by someone on this site.
phoenix code online code editor to test your site and code blocks. this one is neat
onecomplier another online code editor to test your site and code blocks.
html table generator generator that create html tables for you. there's also a generator (table-styler) that styles tables for you.
online webfonts you can get web fonts and copy the links into your stylesheet instead of downloading fonts. helpful for those who want custom fonts on their bearblog, spacehey, toyhouse, etc.
file.garden you can upload your files and generate links for them. catbox.moe is cool too. helpful for image links and custom fonts.
css layout generator this website generates flexboxes, layouts and grids for you. it's helpful for making galleries too.

layout builders and premade layout templates
sadgrl's layout builder if you don't want to make a website from scratch, you can use this generator that creates a whole layout for you.
petrapixel's layout builder same as the one above but with more features
w3docs HTML layout templates very simple premade layout templates
eggramen's layout templates premade layout templates with cool aesthetic themes but you can also style it to your liking.

i will add more links later