Is it supposed to wobble? (Rotor)

[svxjoe]

I was changing my front brake pads today, and when I took off the front right wheel, the rotor was able to move in and out on the hub. Then when I took off the other (left) front wheel, that rotor had no movement at all in and out. Both rotors spun around just fine, but it was the movement in and out of the right front rotor that worries me.

Is this normal?

Or are both rotors supposed to move like this and maybe the one that isn't moving is becuz it's rusted to the hub?.?.?

If I were to remove the entire caliper mechanism, what actually is holding the rotor on?

Any information is appreciated.

-SVXJoe