Easy-Error(Im just new to this)

Hey, so i want to make a plugin, but before i can advance to anything, i just wanted a simple one to make sure it worked so i used as a guide. and it works perfectly for him but when i run my server this is the errors i get..

main:
2011-12-15 19:28:31 [SEVERE] Could not load 'plugins\RegionAlerter.jar' in folder 'plugins':
java.lang.UnsupportedClassVersionError: me/iiiBeastt/region/main : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
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.findClass(PluginClassLoader.java:36)
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:24)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(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:170)
at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:215)
at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:136)
at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:151)
at org.bukkit.craftbukkit.CraftServer.reload(CraftServer.java:434)
at org.bukkit.Bukkit.reload(Bukkit.java:187)
at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:22)
at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:165)
at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:378)
at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:374)
at net.minecraft.server.MinecraftServer.b(MinecraftServer.java:564)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:541)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:425)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:457)

Code:

package me.iiiBeastt.region;

import java.util.logging.Logger;

import org.bukkit.event.Event.Priority;
import org.bukkit.plugin.PluginManager;
import org.bukkit.plugin.java.JavaPlugin;

public class main extends JavaPlugin{
    private final playerlistener pListener = new playerlistener();
    Logger log = Logger.getLogger("Minecraft");
    @Override
    public void onDisable() {
        log.info("RegionAlert has been disabled!");

    }

    @Override
    public void onEnable() {
        PluginManager pm = getServer().getPluginManager();
        pm.registerEvent(org.bukkit.event.Event.Type.PLAYER_LOGIN, pListener, Priority.Normal, this);
        pm.registerEvent(org.bukkit.event.Event.Type.PLAYER_QUIT, pListener, Priority.Normal, this);
        log.info("RegionAlert has been disabled!");

    }

}

Is my code. Any help?

Also this
listener:

Code:

package me.iiiBeastt.region;

import org.bukkit.Server;
import org.bukkit.entity.Player;
import org.bukkit.event.player.PlayerListener;
import org.bukkit.event.player.PlayerLoginEvent;
import org.bukkit.event.player.PlayerQuitEvent;

public class playerlistener extends PlayerListener{
    public void onPlayerLogin (PlayerLoginEvent event){
        Player player = event.getPlayer();
        Server server = player.getServer();
        String playername = player.getName();
        server.broadcastMessage("WELCOME TO VOLTCRAFT!");

    }
public void onPlayerQuit(PlayerQuitEvent event){
    Player player = event.getPlayer();
    Server server = player.getServer();
    String playername = player.getName();
    server.broadcastMessage("COME BACK SOON!");

}
}

Plugin.yml
name: RegionAlerter
version: 0.1
main: me.iiiBeastt.region.main

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

you are compiling it using java 7 but trying to run it using java 6, make sure your java is updated