I've complied my applet file sucessfully but when I hit any button, a long list of errors appear. Can anyone point me in the right direction?

(Sorry, don't know how to do a code box on this board)

//Input Card
JLabel labelInput = new JLabel ("Input", SwingConstants.CENTER);
JPanel inputCard = new JPanel();
inputCard.add (labelInput);
deck.add (inputCard, labelInput.getText());

...other cards declared like this too...

//add listeners
input.addActionListener (this);
admit.addActionListener (this);
display.addActionListener (this);

public void actionPerformed (ActionEvent event)
{

//show cards
if (event.getSource() == input)
cardManager.first(deck);
else if (event.getSource ()== admit)
cardManager.next(deck);
else if (event.getSource()==display);
cardManager.last(deck);