[Help] resolution?

[natinet]

hi.

i cant understand how does the resolution affect pixel bots?
i mean...i have a duplicate picture of kal- same size, now i search the pixerl in the picture, lets say i found it in 50,50: i need to send the message like that:

PHP Code:

IntPtr lParam = new IntPtr(50 * 0x10000 + 50);
IntPtr wParam = IntPtr.Zero;
SendMessage(p, WM_LBUTTONDOWN, wParam, lParam); 


cool : i did so...but it clicks on a place that is not the real place i need !!
so...is it a problem of resolution? or anything other?
thanks alot.