ActiveX controls appear as windowed controls in Internet Explorer, while most other controls (especially in newer versions of IE) are windowless. Flash has a wmode parameter for whether it drew a window without windows or windows, but, in my experience, it is very difficult to achieve, especially if the object is written in .NET and not in C ++.
All window elements are painted on top of all windowless elements, despite the wishes of their container. However, window elements fulfill the z-index attribute relative to each other, just as windowless elements follow the z-index attribute with respect to each other.
All windowless elements are displayed on the same MSHTML plane and window elements are drawn on a separate MSHTML plane. You can use z-index to control elements in one plane, but not mix elements in different planes. You can change the z-index of elements on each plane, but the window plane always draws on top of the plane without a window.
http://support.microsoft.com/kb/177378
There are two possible solutions that I can think of. You can try the iframe "cutout" solution , which explains that you can use iframes to "cut" the part of the HTML plugin below to show.
The second solution is to draw popup menus in the popup object . These are separate windows that appear in front of your web page and may even exceed the borders of the document. with some limitations; the main drawback is that they have no shadows, so this may guess your style a little.