I just replaced one light fixture from a switch that has two fixtures powerd from it, it had only three wires (White, Black, Copper) so I wireed those to the new fixture as suggested by the document, and matched the way the old light was wired, but now niether of the lights work on that switch, I even unwired the new one and put the old one back exactly how it was and still no light, I looked at the circuit breaker outside but it was not tripped, What could I have possibly done to make the lights stop working.

I fixed ;-)