DONT do this. Libc 5.4.x fixes many things, especially security. Instead
do the following (which is akin to how you make netscrap work on digital
unix 4 where the same problems occur)
Unpack libc5.2.18 libc.so.5.2.18 into /usr/local/netscrap/lib. Move
netscape into /usr/local/netscrap/lib
Add a new script 'netscape' that does
export LD_PRELOAD=/usr/local/netscrap/lib/libc.so.5.2.18
exec /usr/local/netscrap/lib/netscape
Now only netscrap uses the old buggy library and you don't inflict it on
the rest of your machine.
Alan