question on iframe position on screen

Dear all,

I don't know if this is the right place to ask this question,
if it doesn't , would you be so kind as to re-route me to the right list?

I'd like to know the position of a certain iframe on screen.

when I access self.screenX I get exactly the same value as if I access top.screenX. 
Why is that? Shouldn't they be different?

As they belong to different orign domains, I am not able to query the parent DOM about its position :(

Any way to solve this issue?

Best,
Oliveiros