Ignition Problems???

I have a 96 Mercury Sable wagon. It was running great until I came out one day and turned on the ignition and no lights lit up on the dash.When I tried to start it I got nothing at all. I've replaced the ignition switch, the ignition cylinder, and the nuetral safety switch. I've checked every fuse and relay in the vehicle. Also the starter, battery, and the ground.None of the new parts are still installed. They didn't fix it , I don't need it. I've done all that I can think of can anyone PLEASE HELP?