Chad Miller / Stupid Mistakes

obvious move?  

This is a tricky play. The tempting response to a hane at the edge is to play over it, at the marked spot. Unfortunately, in this situation those two black stones above ...

hane or not? Consider these stones first.  

... are White's shoe-horn into stealing more territory. If Black responds at , then White has a double-atari to make.

first variation of 4  

White threatens the marked stones and forces black to cover, . White breaks though with .

Not covering at is much worse.

best move  

You'll lose a few more points of territory, but it's the best way out.

The lesson to learn is that two stones alone are much weaker than they seem. One stone away from the edge is tight enough to not have this problem and three stones has enough liberties to survive, but two is a cause of trouble.

Alex Weldon: You're missing one variation that is probably the most important, since it's the least obvious to beginners:

Less obvious variation  

Most beginners would think that the double-atari doesn't work, because Black can capture at . However ...

Less obvious variation (continued)  

White can capture this way.

Anyway, I believe this common mistake is covered somewhere else on the site, but I'm not sure of the page name.