Can a proton ever be destroyed or created? If not, it would be a nice to try to figure out the number of protons in the universe... :)

Protons are formed in β- decay, and decay to a positron, a neutrino and a neutron in β+ decay.

Thats interesting... Do you know any website or source that has more information about that?

Wikipedia is usually a good place to start:
http://en.wikipedia.org/wiki/Beta_decay