Run time problem


When i run a simple program then it shows this message-

WARNING: Could not load properties. Creating a new one.
Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: [Lorg/lwjgl/opengl/DisplayMode;
        at java.lang.Class.getDeclaredMethods0(Native Method)


What is the problem it is?

the lwjgl.jar is not in your classpath