Using Netscape 4.
Can anyone offer me advise on what I'm doing wrong?
But seriously, NN4's CSS implementation is *very* broken. So much so, that your best bet may be to use a completely separate basic style sheet for NN4, then use @import to pull in the full one for other browsers.
This site should help with working out which bits of CSS you can use in NN4 without it wrecking the whole thing.
<link rel="stylesheet" type="text/css" href="path/to/nn4stylesheet.css">
<style type="text/css">@import url(path/to/full.css);</style>