position() in Firefox

position() in Firefox

Hello,
when i want to get the height of some element, i get different values
in Firefox and IE.
The values in IE are the correct values, the Firefox returns greater
values.
I have written a minimal sample:
http://joomla.paradi.de/test.php
$("#div").position().top returns also wrong values in FF.
Is this a known bug, do i a mistake or on most important, do someone
knows a bugfix or a other way?
Marius
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