By default, flash movies are always shown on the top-level of a display tree.
However, it can be very useful to be able to move the flash content to the background, and having it overlapped by other content;
e.g. You have a flash movie in the header of your website, but there’s a sidebar menu which should be displayed over the header.
This is easily achieved by following these steps:
Add wmode="transparent" to your object and embed tags which include the flash movie
Wrap the object and embed tags by a div and assign a CSS class to it.
Define a z-index for this class in your stylesheet.
Assign a higher z-index for all items that should overlay the flash movie.