Java Applet not Working

Ok im trying to play a game on my macbook and it keep says Java applet wont load. And it shows a big red X on the left of the screen and this is what it shows when i click on it was wondering if anyone could help this problem thanks.

Java Plug-in 1.5.0

Using JRE version 1.5.0_30 Java HotSpot(TM) Client VM

User home directory = /Users/aydynelmore

----------------------------------------------------

c: clear console window

f: finalize objects on finalization queue

g: garbage collect

h: display this help message

l: dump classloader list

m: print memory usage

o: trigger logging

p: reload proxy configuration

q: hide console

r: reload policy configuration

s: dump system and deployment properties

t: dump thread list

v: dump thread stack

x: clear classloader cache

0-5: set trace level to <n>

----------------------------------------------------

MRJ Plugin for Mac OS X v1.0.1

[starting up Java Applet Security @ Sat Jan 28 15:52:36 CST 2012]

java.lang.UnsupportedClassVersionError: Bad version number in .class file

at java.lang.ClassLoader.defineClass1(Native Method)

at java.lang.ClassLoader.defineClass(ClassLoader.java:676)

at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)

at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)

at java.net.URLClassLoader.access$100(URLClassLoader.java:56)

at java.net.URLClassLoader$1.run(URLClassLoader.java:195)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:188)

at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:173)

at java.lang.ClassLoader.loadClass(ClassLoader.java:317)

at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:145)

at java.lang.ClassLoader.loadClass(ClassLoader.java:252)

at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:659)

at sun.applet.AppletPanel.createApplet(AppletPanel.java:786)

at sun.plugin.AppletViewer.createApplet(AppletViewer.java:2018)

at jep.AppletFramePanel.createApplet(Unknown Source)

at sun.applet.AppletPanel.runLoader(AppletPanel.java:715)

at sun.applet.AppletPanel.run(AppletPanel.java:369)

at jep.AppletFramePanel.run(Unknown Source)

at java.lang.Thread.run(Thread.java:655)

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

at jep.AppletFrame.destroyAppletDirectly1(Unknown Source)

at jep.AppletFrame$Destroy1.run(Unknown Source)

at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)

at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:499)

at java.awt.EventQueue.access$000(EventQueue.java:80)

at java.awt.EventQueue$1.run(EventQueue.java:462)

at java.awt.EventQueue$1.run(EventQueue.java:461)

at java.security.AccessController.doPrivileged(Native Method)

at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlConte xt.java:84)

at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlConte xt.java:95)

at java.awt.EventQueue$2.run(EventQueue.java:476)

at java.awt.EventQueue$2.run(EventQueue.java:475)

at java.security.AccessController.doPrivileged(Native Method)

at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlConte xt.java:84)

at java.awt.EventQueue.dispatchEvent(EventQueue.java:473)

at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java: 269)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:19 0)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:184)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:176)

at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)

java.lang.UnsupportedClassVersionError: Bad version number in .class file

at java.lang.ClassLoader.defineClass1(Native Method)

at java.lang.ClassLoader.defineClass(ClassLoader.java:676)

at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)

at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)

at java.net.URLClassLoader.access$100(URLClassLoader.java:56)

at java.net.URLClassLoader$1.run(URLClassLoader.java:195)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:188)

at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:173)

at java.lang.ClassLoader.loadClass(ClassLoader.java:317)

at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:145)

at java.lang.ClassLoader.loadClass(ClassLoader.java:252)

at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:659)

at sun.applet.AppletPanel.createApplet(AppletPanel.java:786)

at sun.plugin.AppletViewer.createApplet(AppletViewer.java:2018)

at jep.AppletFramePanel.createApplet(Unknown Source)

at sun.applet.AppletPanel.runLoader(AppletPanel.java:715)

at sun.applet.AppletPanel.run(AppletPanel.java:369)

at jep.AppletFramePanel.run(Unknown Source)

at java.lang.Thread.run(Thread.java:655)