browser, rez, OS issues

Using CSSes requires the web page developer to take into account which
browser (but what doesn't), which OS and what the resolution of the
monitor is. Right?
I mean everything I'vedone with CSSes has required this hoop jumping.

PLEASE - If I got it wrong, let me know! I'll stop putting JavaScript
checking for browser & OS issues onto my pages, and annoying msgs saying,
"This page best viewed at yyy x zzz resolution."

Has there been a "fix" or an acknwledged work around to these issues?

TIA! ...