[answered] i used to see christians forum in this site

There's no exclusively "Christian forum" as such here, oudalone. But there are Christian posters, who often contribute to the Spirituality & Religion forum.

I believe there were 'private' group forums at one time. I don't believe they are currently active or available.

'Christians' is still one of the Non-member groups, but - JPB said so already - not working (since quite some time).

(Though this group seems to be available, at least it's noted on my A2K-site.)