Wow, how'd you get those two sites mixed up? I can't figure out what it says since Google Translate locks up when I try.

  why I cannot login https://support.mozilla.org/en-US/users/login with my mozilla account which registered from https://account.mozilla.com.cn 

SUMO (this site support.mozilla.org) is independent from https://account.mozilla.com.cn/users/register/. I don't even know where you got that from. The correct place to register for an account here to ask a question about Firefox is through the AAQ workflow (posting a question in the support forum by going to /questions/new). Looks like you've already created an account! Your profile page can be reached by clicking https://support.mozilla.org/en-US/user/1084849 or by clicking your username at the top of this page. (see screenshot)

The reason we don't have a sign up link for regular users (people who ask questions) is because we want users who have questions to register through the process of asking a new question. People who want to contribute to Mozilla have their own way of getting to the login page by clicking the "Get Involved" button in the front page (support.mozilla.org)

There are several sites that have similar names, but are independent from each other.

The account.mozilla.com website (and also the account.mozilla.com.cn) website is used by the new Firefox Sync service.

• https://support.mozilla.org/kb/how-to-update-to-the-new-firefox-sync
• https://wiki.mozilla.org/Identity/Firefox-Accounts

To use this forum you need to create an account for the support.mozilla.org website.

Thanks all! I also guess so.