I have noticed that in NS4 the link may not work if located w/in a positioned <div> w/ the left edge set to some value other than 0px. For instance, if the left was set to 60px, NS4 would give me the finger about 60px left of the actual link. I solved the problem by specifying different <div> properties for NS4 from all other browsers.
NS 4 has had problems with mixing tables, layers and hyperlinks for ever. I have not been able to find a fix or a workaround myself, and I do not expect NS will be working on a fix either. It is as if the link action is relative and the link appearance is absolute.
This isn't a css problem. I am testing for ns4 before loading the css sheets so NS4 is only seeing the NS4 style sheet. I don't have control over the clients browser, but they have upgraded to IE 6. However, the client requires that all pages work in NS4.
I don't really expect to fix this, but need an explanation to put on my FAQ Technical Support page. I think Gil's explanation will do. Thanks all.