I would like to levitate an object by using fix magnets mounted on the
floor, the object levitated above using fix magnets in the object. The
magnets on the floor an in the object are directed to each other with
the same pole (so without any electricity). Suppose the magnets on the
floor have a greater surface
then the in the object.
How dot I get this stabilised (without spinning)? What would I need
and how would it look like to have an object of 500g levitated?

You cannot levitate a static object without active stabilization
unless you are using diamagnetic materials. Diamagnetic means that an
applied field induces a field that tries to cancel the applied field.
Pemanent magnets are ferromagnetic, not diamagnetic, so you cannot do
this with pairs of magnets, no matter what their size or shape unless
you move them in some way (like spinning them) or actively stabilize
them. The standard demonstration of diamagnetic levitation is to use a
superconductor and permanent magnet or vice versa, since
superconductors are strongly diamagnetic. With extremely large fields,
you can levitate frogs and other objects that are weakly diamagnetic.
See for example:

http://www.hfml.sci.kun.nl/froglev.html

A GOOFY IDEA:
Suppose you mount the magnets (in the object to be levitated) such
that you have a vertical N/S and also a horizontal N/S. You would need
two horizontal N/S magnets affixed so that they cross one another in
the shape of a plus (+). Since you now have two positive poles and two
negative poles projecting from this +, you will now want to afix two
more N/S magnets to this + so that it becomes a 8-pointed star (*)
Now, the points around the periphery of this 8-pointed star are
alternating, positive, negative, positive, negative, positive,
negative, and so on around the entire hex.

If you mount this project on the floor in a CONTAINER, you can have
the sides of the contain magnetized as well, perhaps pairing up the
negative and positive poles of the horizontal magnets of the levitated
object with the magnets on the walls of the container.

This is just a goofy idea, but it would be interesting to see what
happens. Would the levitated object spin? Maybe not...try it and see.

lg camp at www.webspawner.com/users/editmasters

Hi Igcamp,

Sounds great but I don't understand how you see it. Van you clarify
this more in a better schematic view, something like:

                        ++
                        ++
                   ++-- -- --++
                   ++-- -- --++
                        ++                       
                        ++