function slideshow(start,last,interval) {
  var frame = start;
  var nextframe = start+1;
  Effect.Appear('img1',{duration:.5,from:0.0,to:1.0});
    setInterval(function() {
    Effect.Fade('img'+frame,{duration:.5,from:1.0,to:0.0,afterFinish:function(){
    $('img'+frame).hide();
    Effect.Appear('img'+nextframe,{duration:.5,from:0.0,to:1.0});
    frame = nextframe;
    nextframe = (frame == last) ? start : nextframe+1;
    }});
 },interval);
 return;
};

var prevheadimgnr = 0;
var headimgnr = 0;
function imageChange() 
{ 
 elem = $('headerimg'); 

 new Effect.Fade( elem,  
 { duration: 0.5, from: 1, to: 0, afterFinish: function() { 
 elem.removeClassName('headimg' + prevheadimgnr);  
 elem.toggleClassName('headimg' + headimgnr);  
 new Effect.Appear( elem, { duration: 0.5, from:0, to: 1 } ); 
 } 
 }  
 );

 prevheadimgnr = headimgnr;
 headimgnr++; 
 if (headimgnr > 4) 
 {
   headimgnr = 0;
 }
}