Netscape security problems under windows NT

[Ciarán McDermott]

public void init()
{

ac = getAudioClip(getCodeBase(), "whoopy.au" );
tick = getImage(getCodeBase(), "tick.gif");
cross = getImage(getCodeBase(),"cross.gif");

etc

Help if you can, I'm using the above to get gifs but I get a security error
when running under Windows NT using the Netscape 4 browser.
Do I need to set my levels of security in Netscape ( and how do I do it?) to
get around this problem or what do I have to do.

Thanks in anticipation,
Ciaran