1. Use <param name="wmode" value="transparent">, for IE.
2. Add the wmode="transparent" parameter to the EMBED tag, for FF & Safari.
Example:
<object width="100" height="100">
<param name="movie" value="http://www.lavatica.com/test.swf">
<param name="wmode" value="transparent">
<embed src="http://www.lavatica.com/test.swf" wmode="transparent" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer"
type="application/x-shockwave-flash" width="100" height="100"></embed>
</object>
p/s: tested in IE 6&7, Safari, Opera 9, FF 2.
