<script language="javascript" type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script>
var gizli = true;
$('document').ready(function(){
$('.top20more').hide();
$('.top20button').click(function(){
degistir();
}); 
});
function degistir(){
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		$('.top20button').attr('src','buton-2.jpg');
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	}else{
		$('.top20button').attr('src','buton-1.jpg');
		gizli = true;
	}
	$('.top20more').slideToggle('slow'); 
}
</script>
<img src="buton-1.jpg" class="top20button" />