Help Installing Java runtime env. to work with with a plain Linux browser

[Roger Jargoyhen]

I use Linux Mandrake 8.0 and am a newbie.
I wish i could run java programs smoothlessly on a browser so i can play on
Yahoo chess server.

I downloaded jre 1.3.1. from Sun and installed it on /usr/java/ (took me
some time mainly because i did not succeed easily to extract from
rpm.bin....)
Now i try to get at least one of my three Linux browsers to run Java
applets, that is to say either Netscape 4.71, or Opera 6.02 or good new
Konqueror.

Whatever i try, up to now, Opera and Konqueror don't charge applets.
Netscape stops running after a while and do not work properly.

I understand i must inform each program on the proper path to find either
the Java program or Java plug-in.

In all the documentation I read about it (many pages indeed),
1./ I do not understand what PRECISE action i have to undertake when they
speak about NSX_PLUGIN_PATH, or OPERA_PLUGIN_PATH and
how to set this kind of variable (with Terminal, with browser, else?).
2./ I do not know by the way which PRECISE file i must target for this
purpose.

I tried to do my best but to no avail. Is there a simple way to tune my
browsers so that i can use Java runtime environment ?
I am frustrated because under XP and MSIE, everything goes well... and
simply.