At the end, there was something like acceptable variation in page view for different browsers.
Thanks. Learning web development back then left some deep scars and lasting lessons. I can no longer imagine all the other stuff I haven't retained because I remember stupid browser quirks from nearly three decades ago.
Getting many designs working consistently between IE and Netscape was impossible. The 640px wide left-aligned table layout was popular for years because it was the easiest common denominator that looked acceptable in both browsers.
Take for example VRML, particularly VRML 2.0. I don't remember the software name, but there was a chat system within a virtual world, perhaps running in a browser (1).
1. https://csdl-images.ieeecomputer.org/mags/cg/1999/02/figures...
Netscape 4 is a broad set of releases over several years. It also wasn't necessarily "bad". It was just largely not mindblowingly better than Netscape 3 (for normal users) while using more CPU and RAM.
I also imagine in this context it's incomplete CSS support is problematic. Netscape 3 will ignore properly commented out CSS (mostly) while 4 will try to interpret what it can and choke on the rest. It's box model doesn't conform to where the CSS spec landed so even if you can give it CSS it can handle, your page is broken in every other browser.