What you state is incorrect.
As I said, the mass is a property of any particle. An error on a measurement is one thing, and you can make an error in measuring a mass. This is right. But the mass itself is always well defined.
This is also what special relativity tells us. If you take any elementary particle, its mass is one of its properties. The mass of the photon is zero, no matter what you try.
RE: Einstein was right- Scientists proved Theory of relativity