I still use Netscape 4 where possible, though lazy programming by website developers frequently causes crashes nowadays. I find it useful as a baseline standard; any web page I produce must work in it equally well as in the most 'up to date' browser iterations. Easy to ensure if you can be bothered. Firefox isn't bad, but can be a pain in the arse when plugins are needed. It never seems to be able to find them. Old versions of Netscape always could.