In the late '90s, the time frame this thread is about, it was well known that the layout engines at the time were not dynamic: they could not in general reflow only parts of the page. Everything else I mentioned in the post that triggered this subthread is obvious simply based on browser engine and OS history.
> (Netscape 4/Opera/IE) didn't have a JIT, didn't use hardware accelerated layers, trapped into kernel mode for GDI calls, didn't use accelerated SIMD for painting, and didn't have HTTP 2. It barely had any optimizations for dynamic restyling, so tons of stuff would get reflowed when it didn't have to.
The features of a program = functionality.
So we're getting our wires crossed due to word choice.
In any case, I'll admit this has dragged on long enough. Truce?
It was just faster, better looking, and skinnable. Plus malware stayed hitting IE so there was that too.
And I never mentioned Netscape: it was called Netscrape then and hackers despised it. I used Opera and IE mainly.