CSS offers a number of powerful features that can be tricky to use, or have a number of parameters, so that it's helpful to be able to visualize them while you work on them. This page offers links to a number of useful tools that will help you build the CSS to style your content using these features.
CSS animation - Stylie
- To check the device display information (helpful in responsive web design) - mydevice.io
- CSS Menus - cssmenumaker.com