butON = new Array, butOFF = new Array;
imagesOK = document.images;
isLoaded = false;
loadpics();

function loadpics() {
if (imagesOK) {
	for (i = 0; i <= 8; i++) {
		butOFF[i] = new Image(); butOFF[i].src = 'img/b' + i + '.gif';
		butON[i] = new Image(); butON[i].src = 'img/b' + i + 's.gif';
	}
	isLoaded = true;
  }
}

function on(i) { if (isLoaded) document.images['i' + i].src = butON[i].src;}
function off(i) { if (isLoaded) document.images['i' + i].src = butOFF[i].src;}