var currentImg = 0;   
function detectKey(e) 
{    
	if (!e) { e = window.event; } 
	if ((e.keyCode == 38) && (currentImg > 0)) 
	{      
		scrollImg("up");    
	}    
	else if ((e.keyCode == 40) && (currentImg < 3)) 
	{      
	scrollImg("down");    
	}    
	return false;   
}
   
function scrollImg(dir) 
{    
	if (dir == "up") 
	{      
		currentImg--;    
	}    
	else if (dir == "down") 
	{      
	currentImg++;    
	}    
	var div = document.getElementById("container");    
	if(div!=null)
		div.scrollTop = (currentImg * 300);   
}

document.onkeyup = function(event) 
{ 
	detectKey(event); 
}  


function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      if (oldonload) {
        oldonload();
      }
      func();
    }
  }
}