No, a magnet will not float in mid-air even if there is nothing below it. While magnets can exert an attractive or repulsive force on other magnets or magnetic materials, they do not possess inherent anti-gravitational properties.
The force exerted by a magnet is the magnetic force, which is different from the force of gravity. Gravity is the force of attraction between two objects with mass, while magnetism arises from the alignment of magnetic domains within a material.
In the absence of any external influences, a magnet will be subject to the force of gravity, pulling it downwards. The magnetic force alone cannot counteract the force of gravity and allow the magnet to float. However, if you arrange magnets in a specific configuration, such as using repelling magnetic fields or magnetic levitation systems, it is possible to suspend a magnet in the air against gravity.