Doublehane on the first line

Wrong double hane  

HolIgor: Double hane is usually used to get ahead. More often on the third or fourth line. It is a strong move but requires a little bit of reading. There is a cutting point, so there is some danger.

and must make ko  

KarlKnechtel: I am slightly ashamed to admit that in my earliest attempts at go, GnuGo would catch me with this fairly often - and the ko didn't even occur to me - bye bye four stones.