public function setDeferredPath($dir, $url = null) {
		$dir = realpath($dir);
		
		if ($dir === false || ! is_writable($dir)) {
			throw new InvalidPath('The directory "' . $dir . '" must exists and be a writable');
		}
		
		$this->deferredDir = $dir;
		
		if ($url === null) {
			$this->deferredUrl = str_replace(rtrim($_SERVER['DOCUMENT_ROOT'], DIRECTORY_SEPARATOR), '', $dir) . '/';
		} else {
			$this->deferredUrl = rtrim($url, '/') . '/';
		}
		
		return $this;
	}