The "Sweet spot" aboard the NX-01
The "sweet spot" is a location aboard every starship, as of 2151, approximately halfway between the artificial gravity generator and the bow plate where the gravity cancels out and reverses.
The sweet spot was named by Travis Mayweather, who enjoyed spending time in the area aboard the freighter ECS Horizon and Template:ShipClass starship Enterprise. (ENT: "Broken Bow", "Horizon")
Since this phenomenon has never been mentioned chronologically after this episode, it's impossible to know whether or not it has been corrected in later vessels.