public function size($value, $px) {
		if (!is_numeric($px) || $px < 0 || $px > 2048) {
			throw new InvalidArgumentException("You must pass the size filter a valid number between 0 and 2048");
		}
		else if (strpos($value, $this->baseUrl) === false
			&& strpos($value, $this->httpsUrl) === false) {
			throw new InvalidArgumentException("You must pass the size filter an existing Gravatar URL");
		}
		else {
			return $this->query($value, array("size" => $px));
		}
	}