BODY BACKGROUND will not work. You have to add Flash file in absolute mode and use z-index to put it behind.
Use a DIV tag with the following attributes and insert this code at the end of document before </body>:
<div style="position: absolute; top: 0; left: 0; z-index: 1;"> <OBJECT CLASSID="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" WIDTH="1024" HEIGHT="800" CODEBASE="http://active.macromedia.com/flash5/cabs/swflash.cab#version=5,0,0,0"> <PARAM NAME="MOVIE" VALUE="t1044.swf"> <PARAM NAME="PLAY" VALUE="true"> <PARAM NAME="LOOP" VALUE="true"> <PARAM NAME="WMODE" VALUE="opaque"> <PARAM NAME="QUALITY" VALUE="high"> <EMBED SRC="t1044.swf" WIDTH="1024" HEIGHT="800" PLAY="true" LOOP="true" WMODE="opaque" QUALITY="high" PLUGINSPAGE="http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash"> </EMBED> </OBJECT> </div>
Now copy the ball several times ("Edit" > "Duplicate"). Resize each ball. For each object choose "Intro Animation" and modify duration time to be unique. We have used 2.2 seconds or 1.8 seconds or 5.6 seconds to create an illusion of random falling.
To publish the Flash animation choose "File" > "Export Flash SWF File". Then choose "File" > "View HTML code". Copy the code to integrate the background with your HTML page (you have to add DIV tag manually).
Download source project t1044.zip (1 kb)
Firefox NOTE: The rest of your html code (entire body section) must be in a separate layer:
<div style="position: relative; z-index: 2;"> ...body section... </div>
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