Come on Charlie, just follow the link that staff member Kansha provided in post 17. Correspondence chess (what Erik mistakenly calls "online") and live chess have different rules.
is it cheating to use additional evaluation board ?
Who cares? The "anti-cheating" committee would never find out that you are using one, since your moves are still your moves.
Character is doing the right thing when nobody's looking. There are too many people who think that the only thing that's right is to get by, and the only thing that's wrong is to get caught. ~J.C. Watts
nerd ahh

If using the analysis board is cheating, why is it there, available to players of online chess? Maybe there should be a feature that disables any forward analysis unless both players agree. I think it should stay available for PAST analysis so you can recall your thinking, especially because I usually have a number of games going simultaneously.