Other Websites:
- W3 Schools
- Color Picker
- Can I Use
- Google Fonts
W3 Schools is a great developer resource, and is highly recommended to use to find CSS and HTML features you've never heard about. It also is useful as a guide for elements you have forgotten the syntax of.
The Google Color Picker gives the information for specific colors, so you can add all sorts of awesome colors!
Some browsers may not support some features, CanIUse tells you what is and isn't supported so you know you aren't going crazy. This was useful for me when trying to figure out why my .svg favicon wasn't working in Safari.
Google Fonts lets you choose from a vast variety of fonts and import them into your website, this can help you change the whole vibe of your website!