Classnotfound Exception when Embedding jar with HTML

I have created a simple Minesweeper game using Java in Eclipse. I have used a normal jar (not a runnable jar) to create the jar file.

I did not use init() or any such functions.

Here is the entire code:

import java.applet.Applet; 
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;


public class Minesweeperapplet extends Applet implements ActionListener {

/**
 * 
 */
private static final long serialVersionUID = 1L;

JFrame frame= new JFrame("Minesweeper von Junaid Aslam");

JButton reset = new JButton("Reset");   //declaring reset button - deklaration des 'reset' button

JButton [][]buttons= new JButton[20][20]; //declaring jbuttons for the game - declaring echt buttons fur das spiel

Container grid= new Container(); //container for the grid - Container fur das grid

boolean [][] zero= new boolean[20][20]; //to keep track of all uncovered zeros - um darauf die aufgedeckten zeros zu markieren

int[][] counts = new int[20][20]; //holds the integer count of all neighbouring mines - das Feld beeinhaltet die Informationen uber die Nummer der angrenzenden Minen

final int mine=10; //Final value set for a mine - diese 'final' Variable representiert eine Mine  

int minesSetForGame = 35;//Number of mines in the game - Bestimmung uber die Anzahl der Minen

public Minesweeperapplet(){


    frame.setSize(1000,700);
    frame.setLayout(new BorderLayout());
    frame.add(reset, BorderLayout.NORTH); //inserting reset button in the borderLayout - Hinzufugen des reset buttons zum borderlayout


    reset.addActionListener(this);


    //setting up grid - stellen die Grid ein
    grid.setLayout(new GridLayout(20,20));

    //initialize button grid - initialisierung des button grid
    for(int a=0;a<buttons.length;a++)
    {
        for(int b=0; b<buttons[0].length;b++)
        {
            buttons[a][b]= new JButton();
            buttons[a][b].addActionListener(this);    //listener for left click - Zuhoren auf 'Left Click'
            buttons[a][b].addMouseListener(new Mouse());//listener for right click - Zuhoren auf 'Right Click'
            grid.add(buttons[a][b]);   //adding buttons to the grid - Hinzufugen der buttons zum grid

        }

    }

    frame.add(grid, BorderLayout.CENTER);  //adding the grid to layout -  etablieren des grids in der Mitte
    creatRandomMines(); //creating random mines - Erstellen zufalliger Minen
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
}



public void creatRandomMines(){  //Creating random mines - Erstellen zufalliger Minen

    ArrayList<Integer> list= new ArrayList<Integer>();

    //initialize list of random pairs
    for(int x=0; x < counts.length; x++)
    {
        for(int y=0; y < counts[0].length; y++)
        {
            list.add(x*100+y);

        }
    }

    //reset count and pick 30 mines
    counts= new int[20][20];//for reset

    for(int a=0; a<minesSetForGame; a++){

        int choice= (int)(Math.random()*list.size());//Math.random()*list.size() picks out number from 0 to 399(400=list.size())
        counts[list.get(choice)/100][list.get(choice)%100]= mine;
        list.remove(choice);//removing the choice we have made for the mine
    }

    //initializing count for counting neighbouring mines- Initialliesieren der Berechnung von den Minen in den Nachbarfeldern
    for(int x=0;x<counts.length;x++)
    {
        for(int y=0; y<counts.length; y++)
        {
            if(counts[x][y]!=mine)
            {
            int neighborcount=0;
            if(x>0 && y>0 && counts[x-1][y-1]==mine)//Oben links button
            {
                neighborcount++;
            }
            if(y>0 && counts[x][y-1]==mine)//Links button
            {
                neighborcount++;
            }
            if( y<(counts[0].length-1) && counts[x][y+1]==mine) //rechts button
            {
                neighborcount++;
            }
            if( x>0 && y<(counts[0].length-1) && counts[x-1][y+1]==mine)//Oben rechts
            {
                neighborcount++;
            }
            if(x>0 && counts[x-1][y]==mine)//Oben
            {
                neighborcount++;
            }
            if(x<(counts.length-1) && y<(counts[0].length-1) && counts[x+1][y+1]==mine)//unten rechts
            {
                neighborcount++;
            }
            if(x<(counts.length-1)&& y>0 && counts[x+1][y-1]==mine)//unten links
            {
                neighborcount++;
            }
            if(x<(counts.length-1) && counts[x+1][y]==mine)//unten
            {
                neighborcount++;
            }

            counts[x][y]=neighborcount;
            }
        }
    }

}

public void lost(){//in case we lose the game - Wenn das Spiel verloren ist, zeige alle Buttons

    for(int x=0;x<buttons.length;x++)
    {
        for(int y=0;y<buttons[0].length;y++)
        {
            if(counts[x][y]!=mine)
            {
            buttons[x][y].setText(counts[x][y]+"");
            buttons[x][y].setEnabled(false); //Machen setEnabled=false fur alle nicht Minen buttons
            }
            else{
                buttons[x][y].setBackground(Color.ORANGE);//Markiere alle immer noch zugedeckten Minen orange
                buttons[x][y].setText("X");//Markiere alle immer noch zugedeckten Minen mit "X" String


            }
        }
    }
}

public void zero(int x, int y){ //decke alle angrenzenden zeros auf


     if(zero[x][y]==false)
     {
            buttons[x][y].setEnabled(false);
            buttons[x][y].setText(counts[x][y]+"");
            zero[x][y]=true;   //alle aufgedeckten zeros werden 'true' gemacht

            //aufdecken der felder bis zum 'non-zero'(zahlen) button

            if(x<(counts.length-1)){
            buttons[x+1][y].setText(counts[x+1][y]+""); //fur unten buttons so that they keep opening until the number is not 0
            buttons[x+1][y].setEnabled(false);}

            if(x>0)
            {buttons[x-1][y].setText(counts[x-1][y]+"");//oben
            buttons[x-1][y].setEnabled(false);}

            if(y>0){
            buttons[x][y-1].setText(counts[x][y-1]+"");//links
            buttons[x][y-1].setEnabled(false);}

            if(y>0 && x>0){
            buttons[x-1][y-1].setText(counts[x-1][y-1]+"");//links oben
            buttons[x-1][y-1].setEnabled(false);}

            if( x>0 && y<(counts[0].length-1)){
            buttons[x-1][y+1].setText(counts[x-1][y+1]+"");//rechts oben
            buttons[x-1][y+1].setEnabled(false);}

            if(y<(counts[0].length-1)){
            buttons[x][y+1].setText(counts[x][y+1]+"");//rechts button
            buttons[x][y+1].setEnabled(false);}

            if(x<(counts.length-1) && y>0){
            buttons[x+1][y-1].setText(counts[x+1][y-1]+"");//links unten
            buttons[x+1][y-1].setEnabled(false);}

            if(x<counts.length-1 && y<counts[0].length-1){
            buttons[x+1][y+1].setText(counts[x+1][y+1]+"");//rechts unten
            buttons[x+1][y+1].setEnabled(false);}

            //to clear out all zeros adjacent to zeros already cleared out
            //um alle zeros aufzudecken, die an bereits auf gedeckte zeros angrenzen

            if(x>0 && counts[x-1][y]==0)//oben - Upper button
            {
                zero(x-1,y);
            }
            if(x<(counts.length-1) && counts[x+1][y]==0)//unten - Lower button
            {
                zero(x+1,y);
            }
            if(y>0 && counts[x][y-1]==0)//links - Left button
            {
                zero(x,y-1);
            }
            if(y>0 && x>0 && counts[x-1][y-1]==0)//links oben - upper left button
            {
                zero(x-1,y-1);
            }
            if( x>0 && y<(counts[0].length-1) && counts[x-1][y+1]==0)//rechts oben - right button
            {
                zero(x-1,y+1);
            }
            if(y<(counts[0].length-1) && counts[x][y+1]==0)//rechts - right button
            {
                zero(x,y+1);
            }
            if(x<(counts.length-1) && y>0 && counts[x+1][y-1]==0 )//links unten - lower left
            {
                zero(x+1,y-1);
            }
            if(x<counts.length-1 && y<counts[0].length-1 && counts[x+1][y+1]==0)//rechts unten - lower right
            {
                zero(x+1,y+1);
            }
     }
}


     public void checkforwin() //um zu Kontrollieren ob spieler gewonnen hast
                               //to check if player has won
      {
         int minecounter=0,nonminecounter=0;

         for(int x=0;x<buttons.length;x++) 
            {
                for(int y=0;y<buttons[0].length;y++)
                {

                    if(counts[x][y]==mine)
                    {

                    if(buttons[x][y].isEnabled())
                    {
                        minecounter++; //Wird alle Minen zahlen, die noch nicht angeklickt wurden
                    }                   //will count all mines which have not been clicked on
                    }
                    else if(counts[x][y]!=mine)
                    {
                        if(!buttons[x][y].isEnabled())

                            nonminecounter++; // will count all buttons other than mines which have been shown to the player or clicked on
                                              //Wird alle buttons zahlen, die aufgedeckt sind und keine minen sind 
                    }
                }

                if(minecounter==minesSetForGame && nonminecounter==((counts.length*counts[0].length)-minecounter))
                {//checks if all mines are isEnabled(not clicked on) and all other buttons are !isEnabled()(they are disabled)
                    JOptionPane.showMessageDialog(new JFrame(), "Sie haben Gewonnen.");
                }

     }

}

@Override
public void actionPerformed(ActionEvent event) {

    if(event.getSource().equals(reset)){


        for(int x=0;x<buttons.length;x++) //resets all buttons[x][y]
        {                                   
            for(int y=0;y<buttons[0].length;y++)
            {
                buttons[x][y].setEnabled(true);
                buttons[x][y].setBackground(null);//sets all button background color to default
                buttons[x][y].setForeground(null);
                buttons[x][y].setText("");
            }
    }
        creatRandomMines();//creates mines for restart - erstellt Minen fur den Neustart
        zero=new boolean[20][20]; //machen alle zero zu false noch mal

    }else{

        for(int x=0; x<buttons.length; x++)//ob der Spieler druckt ein andere button
        {
            for(int y=0; y<buttons[0].length; y++)
            {
                if(event.getSource().equals(buttons[x][y]))
                {
                    if(buttons[x][y].getBackground().equals(Color.red) || buttons[x][y].getBackground().equals(Color.ORANGE))
                    {
                        //if the button is flagged or has orange background (after losing) do nothing
                        //Wenn der button 'flagged' ist, konnen wir nichts machen
                    }
                    else if(counts[x][y]==mine)      // if the button is a mine - wenn der angeklickte Button eine Mine ist
                    {
                        lost();//calling lost method because game is lost - das spiel ist verloren
                        buttons[x][y].setForeground(Color.red);
                        buttons[x][y].setText("X");



                    }else if(counts[x][y]==0)// if the clicked button is zero
                    {                       //wenn der angeklickte button zero ist
                        int i=x,j=y;
                        zero(i,j);  //calling zero method
                    }               //rufen zero method


                    else{
                    buttons[x][y].setText(counts[x][y]+"");//sets the clicked button to count[x][y]- einsetzen der nummer bei einem eingeklickten button zu count[x][y]
                    buttons[x][y].setEnabled(false); //disables the button after the click - 'disable' button nach dem Klick
                    checkforwin();//checking for winner after a non-mine button is clicked - prufen der gewinner

                    }
                }
            }
        }
    }

}

public class Mouse extends MouseAdapter { //for right click functionality
                                            // fur rechten Klick Funktionalitat

    @Override
    public void mousePressed(MouseEvent event){
        if(event.isMetaDown())
        {
            for(int x=0;x<buttons.length;x++) 
            {
                for(int y=0;y<buttons[0].length;y++)
                {
                    if(event.getSource().equals(buttons[x][y]))
                    {
                        if(!buttons[x][y].getBackground().equals(Color.red))// if the button is not yet flagged - wenn die button noch nicht 'flagged' ist
                        {
                            if(buttons[x][y].isEnabled()) //to make sure the button is still enabled - um zu prufen dass der button isEnabled() ist
                            {
                                buttons[x][y].setBackground(Color.red);//set color to red if clicked once - stelle die Background farbe Rot ein bei einem Klick

                            }

                        }
                        else{
                            buttons[x][y].setBackground(null);//set color to default if clicked again - stelle die farbe zu Default bei noch einem klick
                            }

                    }
                }
        }


        }
    }


}

}

Here is my complete HTML code:

  <!DOCTYPE html>
  <html>
  <head>
 <title>Minesweeper100</title>


 </head>

 <body>


    <applet code = "Minesweeperapplet.class" archive="Minesweeperapplet.jar"    width=1000 height=700></applet>

 </body>

</html>

Now I am using Filezilla server to upload and run it on Firefox. It says "ClassNotFoundException Minesweeperapplet.class"... everytime I run it.

The .jar:

I have been stuck on it for 2 days. I have read all such questions here but my problem does not seem to go away. The HTML and jar are in the same folder; all file names have been checked and re-checked zillion times. I even had a dream about this error.

PLEASE HELP!!!!!