Their java comrades

On my mac book java console when running a applet on a web browser the following message appears: access denied ( Imagestore read). The applet should pick up some image files from a file folder called Imagestore found in my web folder called webwillem at the userdir (it works just fine on the sun applet viewer).
I am pretty sure the it is the applet.policy that is causing trouble.

-I modified the applet.policy file into:
grant codeBase "file:/webwillem/*" {
(should be modified later to just grant reading for that specific folder Imagestore)
-So my first question is how to setup the content of the applet.policy file correctly.
-And where sits that file in order to work correctly (for the moment it gets copied automatic into my jar-applet file without having much effect I believe).
After having the correct content of the policy file and having it put at the right spot, the applet should work (when I take out e.g. the file download content of the applet, it does appear on my webpage).
Please keep in mind that I work on a mac osx (10.4) system, so pc information, I believe does help me much. Though I even do not really understand where the problem lies. I wonder, can’t these things be a little easier (or is it all a result of big company wars such as sun Microsoft apple etc) or am I just to limited to understand this all.