function preload(i) { 
	var img = new Image(); 
	img.src = i; return img; 
}

preload('images/print-act.gif');
preload('images/identity-act.gif');
preload('images/illustration-act.gif');
preload('images/icons-act.gif');
preload('images/web-act.gif');

function roll(name, mode) {
	if ( mode == 'on' ) m = '-act'; else m = '';
	window.document.images[name].src = 'images/' + name + m + '.gif';
}