Your frontend experience sounds like you've only dealt with web apps. Try making more web sites. That is, collections of pages that have enough content on them

Your frontend experience sounds like you've only dealt with web apps. Try making more web sites. That is, collections of pages that have enough content on them to scroll. Don't use any framework, don't even use JS if you can help it -- maybe something like PHP is ok to avoid some repetition (i.e. just use it for require_once of shared html). Then you'll understand the environment CSS was forged in. Ctrl+F the comments here for "box model" for the main "make it click" piece. (Edit: you might even want to try designing without CSS, to see what that's like. It's actually not that bad, and may well remind you of how things are typically done in frameworks these days -- a regression IMO, but a reminder that separation of design from markup isn't truly necessary.)