function roll(element, val) {
	var img = element.getElementsByTagName('img')[0];
	var src = '';
	var re = /(.*tab_\w+\d)b*(\.jpg)/;
	var match = re.exec(img.src);
	if (val == 'on') {
		img.src = match[1] + 'b' + match[2];
	} else {
		img.src = match[1] + match[2];
	}
}