I remember that as an extremely painful experience. I can't remember all the details, but I remember that until flexbox and grid were implemented, everything CSS related was a pain. I vaguely remember that until 2008-2009 (maybe I'm off by 1-2 years) something trivial as rounded corners also was a pain.
I also remember that about 80% of the CSS pain was caused by Microsoft Intenet Explorer 6.0. It was complete garbage when dealing with CSS and Javascript (I was working with huge JS codebases at the time). But nobody in the web world could ignore it because it had a huge market share. I hate that browser and Microsoft with passion till this day. So many hours, days, weeks wasted to make everything work in a browser that wasn't updated by MS (why spend money when everybody is using it - they even fired the team that worked on it) and had a very "specific" implementation of Web standards.