There are several plug-in dirs available:
	~/.netscape/plugins
	/usr/local/lib/netscape/plugins
	/usr/lib/netscape/plugins
	/usr/lib/netscape/$VER/plugins
	/usr/lib/netscape/$VER/$BIN/plugins

These dirs are only added to NS_PLUGIN_PATH if they exist.  Also
checked are the list of dirs above, with -libc# appended, where #
depends on the libc that netscape was compiled against.

The list can be added/modified by specifing variables in the
environment file.