CSS sections on interviews are always about gotchas. Do you know how this piece works off the top of your head? etc.

Why not test it like we test other coding skills? Style some code, add a new parameter or test, style it again? Talk about what is changing and why?

That would enable you to understand whether the candidate understands things like floats, and also get into the nitty gritty of *why* they style things the way they do and how well they respond to change. It'll also show you if they can think long term about CSS and refactor it!

Most CSS work isn't "can you remember which display type is correct for this situation off the top of your head?" You can google that shit. Most of it is "this new piece of code completely breaks the large and fragile codebase that was painfully cobbled together! how and why?"