Funny _Y value on fullscreen flash

hi

working on a new site, my client asked for a fullscreen flash site. np.

i placed my content window dynamicly with a valid _x _y value.

fe. // edit : i use this in a onResize function

content._x = Stage.width/2;
content._y = Stage.height/2 - content._height/2;

now when i publish in flash the content window shows up nicely.
(so in flash i see an exact fit of my stage)

but when i publish fullscreen in explorer/opera/firefox, my _y value of the content window suddenly changes. > the _y seems to be “higher”.
i publish with the html tag > 100 procent, no scale, and top / left alignment.

(obviously the stage scales, without the content, but still my _y value should be the same right? cuz when you have a stage of 100 or of 300
a Stage.height/2-content._height/2; should ever be the same right?)
it’s confusing for me, i can’t find the logic behind it.

at work now so i can’t post a fla.
but i am sure someone has a explanation to it.

is there a way to prevent this.