public function def($value, $default, $force = false) {
		if (strpos($value, $this->baseUrl) === false && strpos($value, $this->httpsUrl) === false) {
			throw new InvalidArgumentException("You can only a default to existing Gravatar URLs");
		}
		else if (!filter_var($default, FILTER_VALIDATE_URL) && !in_array($default, $this->defaults)) {
			throw new InvalidArgumentException("Default must be a URL or valid default");
		}
		else if (!is_bool($force)) {
			throw new InvalidArgumentException("The force option for a default must be boolean");
		}
		else {
			if (filter_var($default, FILTER_VALIDATE_URL)) $default = urlencode($default);
                        $addition = array("default" => $default);
                        if ($force) {
                            $addition["forcedefault"] = 'y';
                        }
			return $this->query($value, $addition);
		}
	}