Give us more information on what libraries are you trying to use in that applet and what platform are you trying to run this on. I have a strong **feeling** you are not on windows or not using the Sun JRE (of course I could be wrong).
I am trying to access java3d library in applet. They are actully dll files. when I am runnig it through eclipse it works fine but when I am trying to run through HTML over the web it is giving me above mentioned error. I am trying to view HTML on Windows with SUN JRE.