Netscape has some 7 major versions with many subversions in each. It's possible that older versions don't work or your web HTML code isn't passing the HTML validator we see at http://validator.w3.org/
I have a web site that I manage and on the web site I have a page with several thumbnail images that link to larger images. I decided to add a description to the thumbnail images so, I used the ALT function in HTML with the <IMG SRC> tag. A friend of mine visited my site and said he did not see the text that should pop up when you place your cursor over the thumbnail image. He told me he is using Netscape (not sure what version, I am checking on that). Does this function not work with Netscape?