private String formatUrlParameters() {
		List<String> params = new ArrayList<String>();

		if (size != DEFAULT_SIZE)
			params.add("s=" + size);
		if (rating != DEFAULT_RATING)
			params.add("r=" + rating.getCode());
		if (defaultImage != GravatarDefaultImage.GRAVATAR_ICON)
			params.add("d=" + defaultImage.getCode());

		if (params.isEmpty())
			return "";
		else
			return "?" + StringUtils.join(params.iterator(), "&");
	}