>Why does an <object> tag "act" differently than an <img> tag?
Because elements like objects and select menus don't get rendered by
the browser and are passed off to the system or external plugin to
fill in the gaps.
Some more modern browsers can draw over the top of these replaced elements.
Some older browsers can't draw over them at all.
And some (I'm looking at you IE6) can draw over some such elements
(eg. form inputs) but not others (eg. form selects and objects)
>Drop-down menu appears behind media object; now in place of the image.
>Why is this? Can it be fixed?
Windowed Controls Hider will do what you want
Otherwise you will simply have to adjust your design to make sure
that you don't cause that the offending elements are kept out of the
way of any of your CSS-driven drop-down menus.
List wiki/FAQ -- http://css-discuss.incutio.com/
Supported by evolt.org -- http://www.evolt.org/help_support_evolt/