Netscape 4 has real bugs where valid HTML or CSS crashes it or messes up big time.
I would never advocate changing to Internet Explorer. All it's good for is Windows Security Updates (and about half of those are upgrades to MSIE itself...)
Firefox 1.0 is very stable and capable. I use it for everything, on two different operating systems, it's never broken and it's become the official web browser for the whole office where I work.
Susan, can you give an actual URL for a site with "invisible buttons"?