This player was a limper....he limped often into flops and was semi weak...
I face these donk bets often with AK, not sure how to approach it...
PokerStars No-Limit Hold'em, $0.02 BB (8 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

UTG+1 ($9.89)
Hero (MP1) ($2.57)
MP2 ($2.89)
CO ($5.04)
Button ($2.66)
SB ($2.14)
Villain (BB) ($0.78)
UTG ($4.56)

Preflop: Hero is MP1 with A, K
2 folds, Hero bets $0.08, 4 folds, Villain calls $0.06

Flop: ($0.17) 4, 3, 9 (2 players)
Villain bets $0.10, Hero ?

Sure I didn't have anything but I had a hard time believing he had something as well. I suppose he could have 33-TT in his hand, thats what I see lots of these limpers limp with preflop. He prob would have raised with JJ+ preflop. He also could have some high paint cards and think the flop didn't help me at all.

So what do these donk bets mean usually?