CSS2 (Cascading Stylesheets version 2) is a standard, which was specified from the international group for the web W3C
and which descripes the layout of web pages. It was published already 1998, the
version 2.1 (with slight improvements) is also known for years.
Version 3.0 is worked on.
Notwithstanding that there are still browsers today, which dont master this standard. Of course thats true for browsers, which where published for more than 10 years, but unfortunately also for some, which are much newer, and for which their manufacturer distributes patches nearly weekly.
On the other side there are manufacturers, who's browsers master the standard (also version 2.1) since years. These browsers are free available for many platforms, offer often more comfort during surfing and can be installed (provided there is enough free space on the disc) additionally as an alternative.
Therefore I think it is unreasonable to still consider these oldtimers during web design.
If you like to examine yourself how good your browser is you will find a simple test here.
Naturally I cannot warant or guarantee for functioning and smooth usage of alternate browsers. But I can tell you two browsers, which are technically up to date: