Error

2012-01-29 12:16:00 [SEVERE] Could not load 'plugins/MOTD_MOD.jar' in folder 'plugins':
java.lang.UnsupportedClassVersionError: me/icyrelic/com/motdmod/MOTD : Unsupported major.minor version 51.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
	at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:41)
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131)
	at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:285)
	at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:200)
	at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:156)
	at org.bukkit.craftbukkit.CraftServer.reload(CraftServer.java:442)
	at org.bukkit.Bukkit.reload(Bukkit.java:188)
	at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:22)
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:168)
	at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:386)
	at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:777)
	at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:737)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:725)
	at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:33)
	at net.minecraft.server.NetworkManager.b(NetworkManager.java:226)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:100)
	at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:78)
	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:536)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:434)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)