function toggle(id, hover) {
	var element = document.getElementById(id);
	if (typeof element != 'undefined' && element != null) {
		src = element.src;
		last_slash_pos = src.lastIndexOf('/');
		filename = src.substr(last_slash_pos);
		dirname = src.substr(0, last_slash_pos);
		if (hover) {
			if (filename.indexOf('_over.') == -1) {
				filename = filename.replace(/\.([a-z]+)$/g, '_over.$1');
			}
		} else {
			if (filename.indexOf('_over.') != -1) {
				filename = filename.replace(/_over\.([a-z]+)$/g, '.$1');
			}
		}
		src = dirname + filename;
		element.src = src;
	}
}