Bukkit

What steps will reproduce the problem?
1.install
2.run startserver.command
3.read console

What is the expected output? What do you see instead?

What version of the product are you using?
the newest full release just downloaded it

Do you have an error log of what happened?

22:51:19 [SEVERE] Could not load 'plugins/LockPick.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: com/bethkefamily/LockPick/LockPick : 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_6_R2.CraftServer.loadPlugins(CraftServer.java:239)
    at org.bukkit.craftbukkit.v1_6_R2.CraftServer.<init>(CraftServer.java:217)
    at net.minecraft.server.v1_6_R2.PlayerList.<init>(PlayerList.java:56)
    at net.minecraft.server.v1_6_R2.DedicatedPlayerList.<init>(SourceFile:11)
    at net.minecraft.server.v1_6_R2.DedicatedServer.init(DedicatedServer.java:106)
    at net.minecraft.server.v1_6_R2.MinecraftServer.run(MinecraftServer.java:391)
    at net.minecraft.server.v1_6_R2.ThreadServerApplication.run(SourceFile:582)
Caused by: java.lang.UnsupportedClassVersionError: com/bethkefamily/LockPick/LockPick : 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)
    ... 9 more

Please provide any additional information below.

Are you using Java 6 or 7?