FAILURE TO CHECK NOTAMS AND POOR RWY MARKINGS LEAD LJ25 FLT CREW TO LAND ON CLOSED RWY.

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BEFORE CANCELING IFR; WE STARTED MAKING STANDARD CALLOUTS ON UNICOM. AFTER CANCELING IFR; WE MADE MANY POS RPTS AND ANNOUNCING OUR APCH TO LAND RWY 8 ON UNICOM. RWY 8 WAS CHOSEN DUE TO WINDS. JUST PRIOR TO TOUCHDOWN WE NOTICE DIRTY ORANGE CAUTION CONES GOING UNDERNEATH THE ACFT WHICH RESEMBLED A DISPLACED THRESHOLD. IMMEDIATELY AFTER SEEING THE CONES WE LOOKED DOWN THE RWY FOR A BIG WHITE 'X' SIGNIFYING A POSSIBLE CLOSURE. NOT SEEING ANY 'X;' EQUIP; CONSTRUCTION; OBSTRUCTIONS; PERSONNEL; ETC; WE DETERMINED THAT IT WAS SAFE TO COMPLETE THE LNDG. WHILE COMING TO A STOP; SOMEONE ANNOUNCED THAT WE HAD LANDED ON A CLOSED RWY ON THE SAME UNICOM FREQ THAT WE WERE MAKING ANNOUNCEMENTS AND POS RPTS ON. ONCE PARKED AT THE RAMP WE ASKED THE FUELER ABOUT AN 'X' ON THE RWY AND HE ALSO CONFIRMED THERE WAS NONE. THE NOTAMS WERE CHKED PRIOR TO DEPARTING TO MAI AND FOR SOME REASON THE RWY CLOSURE WAS OVERLOOKED. ALTHOUGH WE NEED TO BE MORE THOROUGH WHEN CHKING THE NOTAMS; THERE SHOULD HAVE BEEN A LARGE WHITE 'X' ON THE RWY INDICATING ITS CLOSURE. EVEN THE SAME CONES IN AN 'X' FORMATION WOULD HAVE PREVENTED THE SITUATION. ALSO; THE CONES DID NOT CONTRAST ENOUGH FROM THE RWY COLOR AND DID NOT BECOME VISIBLE UNTIL SHORTLY BEFORE TOUCHDOWN AND EVEN THEN APPEARED TO BE A DISPLACED THRESHOLD. OTHER THAN THE PREVIOUSLY MENTIONED OCCURRENCE; THE LNDG WAS NORMAL AND UNEVENTFUL. FBO EMPLOYEE INFORMED US THAT A LIGHTNING STRIKE REPAIR HAD PREVIOUSLY BEEN COMPLETED ON THE DEP END OF THE RWY; BUT THEY HAD NOT OFFICIALLY REOPENED IT.