Netscape 4.73 is not HTML 4.01 compatible and has many proprietary Tags - it actually was a pretty poor browser. The later versions of Netscape are much better. Netscape 4.73 specifically does not Support CSS in external style sheets, which is why my site renders wrong.
Although I don't use Netscape, I'm reasonably sure the later versions work fine. I made The decision to upgrade my site to HTML 4.01 and stop supporting Browsers which are not W3C compliant (IE 6 is W3C compliant).
I actually use Opera and IE mostly. Opera is a nice browser, But it doesn't always render sites correctly. My experience is that IE6 virtually always renders sites correctly. I don't use Netscape 7 (formerly Mozilla) because I've found it very unstable and Slow.