z-index: -1
z-index tells the layout the "depth" of an element. When elements overlap, elements with a lower z-index are displayed underneath elements with a higher z-index. All elements have a default z-index of 0. So give your <div> containing the SWF a lower z-index so it should display underneath the other elements on the screen.
Also, the "top: -30" style would, I think, cause the top-left corner of the element to be flush with the left side of the window, but 30 pixels ABOVE the top of the window (effectively being offscreen). That might be appropriate for your SWF, but I don't know.