Coordinates in flash question?

can someone tell me a good tutorial about the coordinates in flash…

i have some probs wit it…

e.g. a movieclip named mc1 has x coordinates 50 and y coordinates 60

in another movieclip named mc2 … i want to change the position of mc1…i use for example in mc2…
onClipEvent(load){
_parent.mc1._x=60;
}

but the mc1 is not position with x coordinates 60 but something else…