thanks @craigb for your reply.
So feedback and forum uses same id and password===OK i got it.
Because you are a "Überevangelist" do you have the authority to delete my forum account ?
I m just asking for knowledge.
I dont want to delete my any of avast accounts.
i raised this question because................
Last night i spent about 4 hour to figure out what happen to my feedback account.
the problems begins when i change my email id on the forum account.
finally this morning i recover my feedback account, (by reverting back the old email id somehow)
Now my both account working fine.