Different positioning on PC and Android

I’ve got a problem with my android “game”. Its just a simple button in the center of the screen using Screen.width/2 and Screen.height/2 for positioning. If i try different resolutions on my pc it works fine and the button is always in the center of the screen. But when i build the program and start it on my smartphone (LG Optimus 4x hd) the button is on the left side of the screen and not in the center anymore.

What am I doing wrong? Doesnt Screen.width and Screen.height work on android or whats wrong and how can i solve this problem?

I think the problem is in the inspector .Take all are private. Once u take public the variable are place are fixed.