Censors frequently notify users that a specific posting "was deleted according to relative laws and regulations".
LinkedIn said it did notify users by showing everyone a banner message alerting them that its privacy policy had changed.
"So starting today we'll notify users in mainland China when they enter a keyword that may cause connection issues".
Field Trip, for instance, uses location awareness to notify users of interesting landmarks, features and places in the real world.
For instance, it will notify users of the change with banners on Google's home page, in search results, in Google Plus notifications and elsewhere.
And it said it would also try to notify users whose posts had been withheld by sending them an e-mail with an explanation.
The directive also requires carriers to notify users of security breaches, like hacker attacks and identity theft, that could jeopardize their privacy.
In contrast, Twitter's policy "is to notify users of requests for their information prior to disclosure unless we are prohibited from doing so by statute or court order".
The same law requires websites to notify users on their first visit to a site that it uses cookies, requesting consent to do so.
