Type of spot I should be check/folding? Someone had to smash this board?

Full Tilt Poker $0.05/$0.10 No Limit Hold'em - 6 players
The Official 2+2 Hand Converter Powered By DeucesCracked.com

Hero (SB): $10.05
BB: $10.50
UTG: $5.75
MP: $18.25
CO: $9.05
BTN: $13.05

Pre Flop: ($0.15) Hero is SB with A J
UTG calls $0.10, 1 fold, CO calls $0.10, 1 fold, Hero raises to $0.50, BB calls $0.40, UTG calls $0.40, CO calls $0.40

Flop: ($2.00) J 4 9 (4 players)
Hero ???

I would bet more pf. I think to 0.7 or maybe 0.8 cause we are here OOP.
In this multiway pot on flop I think I check/call flop if someone bets and reevaluate hand on turn.

I'm not check/folding that, you're definitely ahead of their range, but it's an annoying spot. I'd say bet/fold flop (since any raise is probably a setminer or some godawful two pair), and if you get more than one caller, maybe pot control and check/call any non-heart turn. But if you bet 2/3s and only get one caller, continue to value bet. Most hands that flat are behind you: TT, jacks with worse kickers, A9, Axh, and a few more random suited hands, so there's nothing wrong with leading out.

But I really do hate when I have that kind of hand and get loads of callers, because that's a costly c-bet.

EDIT: I think your PFR is fine, it's 3x + 1 for each limper, which is a standard smallball raise. You could even go as low as .45 here without being strictly wrong, depends on how loose the table tends to be.

What exactly about this board makes you thinking someone has it "smashed?"

There's no way you can check fold this. You're at the top of your range (and way ahead of theirs), bet 1.40 here for value, there's not much at all that beats you other than 44 and 99.

um. bet?

fold what answers are you waiting? WHY THE **** would you play the hand in first place if you hit ur pair, with top kicker, and you want to check or what, ofcourse raise ?

bet 3/4 pot.

The raise size is just fine from the SB , be aggressive on the flop and THEN reevaluate.

No it's too small. 4x + 1 for every limper minimum, which would be $0.60. If they're really cally (or if the BB is a station) you should go even larger.

On that board you're beating JT/QJ/KJ and alot of draws will call your flop bet with incorrect odds (as long as you're betting the turn aswell). I cbet full pot here and shove turn. I also call a shove on the flop because it's easier to flop a draw than a monster on this board.