Null Pointer Exception problem

On some web sites I get an X where there should be a link or links or banner. At the bottom of the page it will sometimes say: Exception:Java.Lang.Null Pointer Exception.
I have downloaded the latest version of Java but it did not help. Any advice would be greatly appreciated. Thank you.

Hi:
This is a Java question (not JavaScript), so I'm moving it over to the Computer Programming forum...

A Null pointer exception occurs when a java program tries to send a message to an unitialized object. Its a problem with the applet's code, not your computer or browser.