I follow the steps in document to setup a custom login page for my domain.

It works, however I would like to force the language to English (now it shows Chinese) in the custom login page. 

I know that can change language for accounts, but how to do that before login?

Furthermore, just for interest, seems that the language used in zoho pages before login which is auto-detected.

I would like to know zoho how to detect language. 

is it by IP or some how by browser setting?

Thanks.