Netscape Twiddles

To launch other applications externally rather than inside the browser
it should be easy, such as for pdf:

preferences -> Navigator -> applications

find pdf in the list and then select the application you want, but.....   
something is missing to stop it working = "%s".

You can add a %s to the application when you choose it or you can
just edit your ~/.mailcap file:

#mailcap entry added by Netscape Helper
application/pdf;acroread %s
#mailcap entry added by Netscape Helper
application/postscript;gv %s