The Java support.

The Java support for the Netscape and Internet Explorer browsers.

Netscape 3.x and Internet Explorer 3.x have the bield-in support for JDK1.0.
Netscape 4.x and Internet Explorer 4.x and above have the bield-in support for JDK1.1.
The applets written by Java 2 (JDK1.2) haven't any support for these browsers yet.
So you should setup the plugins if exist.
You can download JRE-plugins from Java Sun MicroSystem server.