I changed this post from gabe theorem because he actually said the opposite. But this hand has some use so i'm might as well post it.

A lot of people see a post where someone calls down a bluff and they really don't understand what's going on. Just wanted to show you a common bluff that you can easily pick off more.

POKERSTARS GAME #9121100208: HOLD'EM NO LIMIT ($1/$2) - 2007/03/27 - 19:37:34 (ET)
Table 'Silke II' 6-max Seat #3 is the button
Seat 1: Javanut ($231.25 in chips)
Seat 2: sugawolf17 ($185.75 in chips)
Seat 3: suave720 ($129 in chips)
Seat 4: HHHthegame88 ($223.60 in chips)
Seat 5: toska82 ($120.25 in chips)
Seat 6: redgrape ($218.50 in chips)
HHHthegame88: posts small blind $1
toska82: posts big blind $2
*** HOLE CARDS ***
Dealt to redgrape [Ah Js]
redgrape: raises $6 to $8
Javanut: folds
sugawolf17: folds
suave720: folds
HHHthegame88: folds
toska82: calls $6
*** FLOP *** [2c 9s 5d]
toska82: checks
redgrape: bets $12
toska82: calls $12

This could be a lot of hands, top pair, mid pair, bottom pair, overs, straight draws. stronger hands like two pair or a set would probably raise, but possibly not. alot of donks c/r a 9 here.
*** TURN *** [2c 9s 5d] [9c]
toska82: checks
redgrape: checks

this doesn't really tell me anything since he's probably checking every hand here since he's OOP. Although there is a slight possibility that a 9 would lead out.
*** RIVER *** [2c 9s 5d 9c] [Ks]
toska82: bets $48

Ok here's why this bet is so fishy. He makes a very strong bet. However, a hand like a pair of 5's or 2's would be scared of a K, those hands would not bet this strong here. a 9 would probably value bet, although it is definitely capable of this bet. A pair of kings probably doesn't make this bet either, although it could. I have like 1.9:1, i only need to win a little under 35% of the time. Making this an easy call.
redgrape is connected
redgrape: calls $48
*** SHOW DOWN ***
toska82: shows [7s 8s] (a pair of Nines)
redgrape: shows [Ah Js] (a pair of Nines - Ace kicker)

So there, i didn't waste a post.