[Bulldog]

It depends. I don't like the size of your initial flop semi-bluff (20 into a 16 pot could be construed as suspicious), but the bottom line is that it was a failed bluff attempt. You need to know your opponent well enough to know what percentage of the time it will work. After he called the 20, there was 56 in the pot and you bluffed 40. Will your bluff work 44% of the time? If so, good play, too bad you got caught. If he called you with middle pair unknown kicker, it probably won't work 44% of the time, so bad play. More likely he picked up a tell.