AdvancedECO error

2013-02-02 16:32:37 [INFO] Starting minecraft server version 1.4.7
2013-02-02 16:32:37 [INFO] Loading properties
2013-02-02 16:32:37 [INFO] Default game type: SURVIVAL
2013-02-02 16:32:37 [INFO] Generating keypair
2013-02-02 16:32:38 [INFO] Starting Minecraft server on *:25565
2013-02-02 16:32:39 [INFO] This server is running CraftBukkit version git-Bukkit-1.4.7-R1.0-b2624jnks (MC: 1.4.7) (Implementing API version 1.4.7-R1.0)
2013-02-02 16:32:39 [SEVERE] Could not load 'plugins\AdvancedEco.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: me/rjp2525/adveco/AdvancedEco : 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_4_R1.CraftServer.loadPlugins(CraftServer.java:239)
	at org.bukkit.craftbukkit.v1_4_R1.CraftServer.<init>(CraftServer.java:217)
	at net.minecraft.server.v1_4_R1.PlayerList.<init>(PlayerList.java:55)
	at net.minecraft.server.v1_4_R1.DedicatedPlayerList.<init>(SourceFile:11)
	at net.minecraft.server.v1_4_R1.DedicatedServer.init(DedicatedServer.java:104)
	at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:399)
	at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
Caused by: java.lang.UnsupportedClassVersionError: me/rjp2525/adveco/AdvancedEco : Unsupported major.minor version 51.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(Unknown Source)
	at java.security.SecureClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.defineClass(Unknown Source)
	at java.net.URLClassLoader.access$000(Unknown Source)
	at java.net.URLClassLoader$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(Unknown Source)
	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(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClassInternal(Unknown Source)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Unknown Source)
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:173)
	... 9 more
2013-02-02 16:32:39 [INFO] [Vault] Loading Vault v1.2.22-b277
2013-02-02 16:32:40 [INFO] [Vault] Enabling Vault v1.2.22-b277
2013-02-02 16:32:40 [INFO] [Vault][Permission] SuperPermissions loaded as backup permission system.
2013-02-02 16:32:40 [INFO] [Vault] Enabled Version 1.2.22-b277
2013-02-02 16:32:40 [INFO] Preparing level "world"
2013-02-02 16:32:41 [INFO] Preparing start region for level 0 (Seed: 1095272069066627744)
2013-02-02 16:32:42 [INFO] Preparing spawn area: 16%
2013-02-02 16:32:44 [INFO] Preparing spawn area: 16%
2013-02-02 16:32:45 [INFO] Preparing spawn area: 48%
2013-02-02 16:32:46 [INFO] Preparing spawn area: 93%
2013-02-02 16:32:46 [INFO] Preparing start region for level 1 (Seed: 8702036343113850275)
2013-02-02 16:32:47 [INFO] Preparing spawn area: 40%
2013-02-02 16:32:48 [INFO] Preparing spawn area: 73%
2013-02-02 16:32:48 [INFO] Preparing start region for level 2 (Seed: 8702036343113850275)
2013-02-02 16:32:49 [INFO] Preparing spawn area: 48%
2013-02-02 16:32:49 [INFO] Server permissions file permissions.yml is empty, ignoring it
2013-02-02 16:32:49 [INFO] Done (9.247s)! For help, type "help" or "?"
2013-02-02 16:34:09 [INFO] CONSOLE: Stopping the server..
2013-02-02 16:34:09 [INFO] Stopping server
2013-02-02 16:34:09 [INFO] [Vault] Disabling Vault v1.2.22-b277
2013-02-02 16:34:09 [WARNING] DSCT: socket closed
2013-02-02 16:34:09 [INFO] Saving players
2013-02-02 16:34:09 [INFO] Closing listening thread
2013-02-02 16:34:09 [INFO] Saving worlds
2013-02-02 16:34:09 [INFO] Saving chunks for level 'world'/Overworld
2013-02-02 16:34:11 [INFO] Saving chunks for level 'world_nether'/Nether
2013-02-02 16:34:12 [INFO] Saving chunks for level 'world_the_end'/The End
2013-02-02 16:34:12 [INFO] Stopping server