You don't need to know every HTML element. I just use this excellent reference all the time.
Super useful reference, gives you HTML entity name, numeric code, hex code and ISO code.
As with HTML, you don't need to know every CSS property. Use this reference instead.
Another excellent CSS reference, this time from Codrops. Make sure to check this one out, too.
Up-to-date browser support tables for front-end technologies on desktop and mobile browsers.
I find myself using this handy list of the 30 most important CSS selectors from Tutplus all the time.
Excellent guide on how to write better, cleaner and more reusable CSS code.
An amazing collection of easing functions to be used in CSS transitions and animations.
Another reference by MDN, this one is for JavaScript. This is pretty advanced stuff.
This is my personal fav reference for JS, I use this all the times.
Well I don't follow this 100%, it's good to have a style guide to write better code.
List of free fonts, from vintage-inspired typefaces to slab serifs, for a range of projects.
Amazing resource to learn about typography. Learn typography basics in less than 30 minutes.
Don't know what colors to use for your website? Colorhunt helps you with beautiful color palettes.
Collection of beautiful color gradients for you to choose from and export to your project.
Yet another set of colors, inspired in material design. Generate and download your palette.
Easily create lighter and darker versions of any base color. Perfect for hovers, borders and gradients.
Another excellent and popular set of color pallettes. Great selection of colors for all your projects.
My #1 resource for free high-resolution photos. There are more photos here than you can imagine!
Another great resource for free stock photos and videos, created by photographers around the world.
Generate random user data, including photos. Like Lorem Ipsum, but for people.
Hundreds of free and open-source illustrations for your websites, and colors are even customizable.
A highly popular icon font, consisting of 1000+ icons spread across countless categories.
The biggest programmer community. Ask and find answers to HTML, CSS and JS questions.
Excellent articles, guides, and even an almanac, all about front-end development, with a focus on CSS.
A place where front-end developers can ask questions, share links, and show their work.
Easy tool to test your webpage for performance. You can also use it in Chrome DevTools (Lighthouse).
Another tool to compress up to 20 JPEG and PNG images while keeping a good level of quality.
Just upload an image and this tool creates favicons for your website for all platforms.
Popular checklist to check if your website's code is actually ready for deployment.
Another checklist, this one is to catch common usability problems of your website.
An excellent guide to optimize your webpage speed. This is something many devs overlook!
Get a SEO review of your website to address common issues, and get ahead of your competition.
Get free insights about website traffic, visitors and conversions. A must for every website.