var n = 9;
var f = false;
var b = new Array;

function prel()
{
	if(document.images)
	{
		for(i=1;i<=n;i++)
		{
		  str = 'buttons/b' + i + '_o.jpg';
		  b[i-1] = new Image();
		  b[i-1].src = str;
	      }
		f = true;
 	}
}


function on(im)
{
   if (document.images && (f == true)) 
   {
	document.images[im].src="buttons/"+im+"_o.jpg";
   }
}


function off(im)
{
  if (document.images && (f == true)) {document.images[im].src = "buttons/"+im+".jpg";}
}