Why can't I castle?

http://www.chess.com/echess/game?id=119479258

I play Black, and I'm trying to castle the King with the Rook. Why is it not possible? Are they threatened?

It is an active game so no one is allowed to give you advice.

 Sorry.

Suggest you read the rules on castling. While I don't think it is actually giving you advice, I will withhold the reason in deference to notmtwain.

Would this not be the same as asking an arbiter a question?

Castling rules 101--the rook MAY castle through or off of an attacked square. For instance, in a rare instance where a guy has his king on d8 and you have your king on e1 and your rook on a1 and he just took a pawn with his rook on b2, then you may castle with check winning your opponent's rook. You MAY castle in such that your opponent's king will be in check as a result. The king MAY NOT castle through, off of or onto an attacked square. Note where your opponent's queen is. This is why you cannot castle.

How do you paste in games like that?

If I'm going to ask for advice I would've said something along the lines of "what should I play next?" But I've already made the decision to castle and I won't back down and settle for another move. So to all who think I'm looking for a cheat or something, no I'm not, and I've already made up my mind on my desired move.

I didn't suggest you were trying to cheat. I simply said no one is allowed to give you advice. Explaining the rules of chess to you could be considered giving you advice.  

Others have already taken pity on you, however, and have attempted to explain the rules. It's up to you.

You, the king, are sipping tea with your soldiers in the battlefield. Its getting dark and you want to head back to the safety of your castle.

However, intelligence reports confirm that there are attackers who lie in wait to ambush you on your way back castle. Under these circumstances, would you head towards castle or defer your 'castling' plans and share the tent with your soliders?

By the way, are we not allowed to refer to opening gamebooks, endgame books etc. while playing a correspondence game. How is that not 'advice'?

Because you do the work yourself not ask other people to do it for you. I once showed a chess-playing friend of mine an interesting position in a correspondence game that I was playing. He found it very difficult not to give me advice, which I insisted he did not. I have never shown him another correspondence game. We do not talk about chess.

So by clearing my doubts for a move I've already decided on, I'm seeking "advice" eh? Sure, I was asking for advice then. I rest my case. Thank you for your time, you all.

Let's be realistic people--the game he's in right now is not for money, he's clearly new to chess and is unaware of the rules. I do not think his opponent would think it is cheating for him to be clarified on the rules of chess in a forum like this. I think his opponent would find it cheating if we had a discussion to decide what he should play next against his opponent.

I think the part of this rule that people get confused about is that the King can't pass through a square that's attacked by another piece. 

1. The castling must be kingside or queenside.
2. Neither the king nor the chosen rook has previously moved.
3. There are no pieces between the king and the chosen rook.
4. The king is not currently in check.
5. The king does not pass through a square that is attacked by an enemy piece.
6. The king does not end up in check. (True of any legal move.)