A list of all HTML tags with practical examples, really useful. In fact, the whole W3schools website is very useful for learning HTML and CSS. I recommend it.
Choose any color you want with this cool RGB color picker tool! Not only it gives you the HEX value of the color you want, it also shows you other options with differences in brightness, hue and saturation. Pretty cool, right?
RGBA?? What's that? While RGB displays colors with red green and blue, RGBA includes an extra channel that allows you to display the opacity of your color! (That means you can control the transparency of the color)
A website with tutorials for HTML, CSS and JavaScript. Beginner friendly!
You see all those super cool decorative titles? They were all made in this super cool website called Cool Text! You should totally check it out too!!
sadgrl's website has a page dedicated for resources to help build a website, such as guides and layout assistance. For example, some of the background images for this website I downloaded from her archive of tiled backgrounds. I recommend you check her website out, there are plenty of stuff.