Hi
I think I saw somthing like that but I can`t find it.
I want to disallow visitors from seeing the forums, but let robots see it like members.
My version is 3.5.4
Can any body help me with that?

There is a hack at vb.org that will allow it I think.

Caution though: Many people are going to argue that this is considered "Cloaking", I would tend to lean toward agreeing with them. Not something I would do.

Ok,I post thread there ...
I know it may be risk to doing that ,but It will be for little time. I have to do this now and I don`t want to lose google trust.

Cloaking is a VERY risky black hat SEO technique. Don't fool yourself into thinking that Google won't catch you.