Bukkit

What is the expected output? What do you see instead?
Nothing happens. I placed the LittleRpg.jar in my plugins folder and when i start the server literally it does not work. A LittleRpg folder is NOT created and when i do /plugins it doesn't show up in the list O.o

What version of the product are you using?
1.5.2 R1.0

Do you have an error log of what happened?
Nothing about the plugin shows up in the console.

Please provide any additional information below.
Im using the latest recommended build for craftbukkit 1.5.2

If you could help me it would be great, hopefully it isn't some random noob mistake i've done... I've owned servers since beta so I (usually) know what I'm doing... :3

Edit*

I can't do /addrpgworld and I also found a console error message:

19:55:48 [SEVERE] Could not load 'plugins/littleRPG.jar' in folder 'plugins' org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: littlegruz/arpeegee/ArpeegeeMain : Unsupported major.minor version 51.0 at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:184) at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:305) at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:230) at org.bukkit.craftbukkit.v1_5_R3.CraftServer.loadPlugins(CraftServer.java:239) at org.bukkit.craftbukkit.v1_5_R3.CraftServer.<init>(CraftServer.java:217) at net.minecraft.server.v1_5_R3.PlayerList.<init>(PlayerList.java:55) at net.minecraft.server.v1_5_R3.DedicatedPlayerList.<init>(SourceFile:11) at net.minecraft.server.v1_5_R3.DedicatedServer.init(DedicatedServer.java:106) at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java:382) at net.minecraft.server.v1_5_R3.ThreadServerApplication.run(SourceFile:573) Caused by: java.lang.UnsupportedClassVersionError: littlegruz/arpeegee/ArpeegeeMain : Unsupported major.minor version 51.0 at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631) at java.lang.ClassLoader.defineClass(ClassLoader.java:615) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141) at java.net.URLClassLoader.defineClass(URLClassLoader.java:283) at java.net.URLClassLoader.access$000(URLClassLoader.java:58) at java.net.URLClassLoader$1.run(URLClassLoader.java:197) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at org.bukkit.plugin.java.PluginClassLoader.findClass0(PluginClassLoader.java:80) at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:53) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:249) at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:173)