Here is a blog post that explains this issue
Flash content and z-index
Use
<param name="wmode" value="transparent">
From Flash OBJECT and EMBED tag attributes
wmode
Possible values: window, opaque, transparent. Sets the Window Mode property of the Flash movie for transparency, layering, and positioning in the browser.
* window - movie plays in its own rectangular window on a web page.
* opaque - the movie hides everything on the page behind it.
* transparent - the background of the HTML page shows through all
transparent portions of the movie, this may slow animation performance.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…