function rollover(link) {
	eval('document.'+link+'.src = '+link+'_on.src');
}

function rollout(link) {
	eval('document.'+link+'.src = '+link+'_off.src');
}

function preload_images(name_array,img_prefix) {
	var j = name_array.length;
	for (var i=0; i<j; i++) {
		var img_obj = name_array[i];
		eval(img_obj + '_on = new Image()');
		eval(img_obj + '_off = new Image()');
		eval(img_obj + '_on.src = "img/'+img_prefix+img_obj+'_on.gif"');
		eval(img_obj + '_off.src = "img/'+img_prefix+img_obj+'.gif"');
	}
}