can't castle - won't castle

can anyone explain why I cant castle in this game - 329901 - I can't see I'm moving into or out of check... Is there a rule I never learnt?

Game 329901

Your King cannot cross a square that is under attack. The f1 square is being attacked by the pawn.

You can not castle through a check either. The pawn on g2 attacts the f1 square that your king would have to cross to castle.

cheers guys! I've learned something today :-)

Also, just so you know... your Rook can go through an attack when you castle... just not the King.

...and just another little rule: You cannot castle to get out of 'Check'