btnOn = new Array();
btnOff = new Array();
function preload(){
 	for(i=0;i<6;i++){
   		btnOn[i] = new Image();
			btnOff[i] = new Image();
   		btnOn[i].src = "images/btn"+i+"_on.gif";
   		btnOff[i].src = "images/btn"+i+"_off.gif";
	}
}

function On(i){
   	document.images['btn'+i].src = btnOn[i].src;
}
function Off(i){
   	document.images['btn'+i].src = btnOff[i].src;
}