Some CSS features are turned off by default, and can be turned on by changing a preference in about:config. Rather than read through a list of css*enabled preferences with potentially ambiguous names, it's probably best to find the CSS property you want to experiment with on MDN and check the browser compatibility table at the bottom to discover the corresponding preference, if any. For example, to use basic shape parameters for clip-path, you need to toggle the '''layout.css.clip-path-shapes.enabled''' preference. See: https://developer.mozilla.org/docs/Web/CSS/clip-path If you do want to view that list of CSS preferences, you can as follows: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button promising to be careful. (2) In the search box above the list, type or paste '''css*enabled''' and pause while the list is filtered (3) If you click the Value column heading, the enabled=false preferences should sort to the top for easier spotting

That is helpful, thank you.