Who me?

As Will moves closer to his first birthday, and closer to being a toddler and not a baby, he is also moving closer to the tantrum stage, and the understanding of the word "no". He is big into doing things he knows he shouldn't do, and then turning around with a little grin on his face to wait and see if I'll tell him no. We've been using no, and stop so far with him, and he is actually starting to listen to them a little. Today he crawled ever so slowly over to the fireplace and sat down on the hearth and just kind of looked at it. Then he turned towards me and put his hand on the glass.... I told him no and he removed his hand and gave me this innocent look like "what did I do?" and then proceeded to put his hand on it again. I did the same thing, and received the same look. I swear, disciplining him is just so hard when he is so freakin cute!!