I believe you need to include <embed></embed> tags for Firefox/Netscape browsers to read the embedded object code. Try this code along with what you already have:
<object width="638" height="350" classid="clsid

27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=5,0,0,0"><param name="movie" value="http://home2.scarlet.be/alleycat/intro.swf" />
<param name="quality" value="high" />
<param name="bgcolor" value="#000000" />
<embed src="http://home2.scarlet.be/alleycat/intro.swf" " quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="638" height="350"></embed>
</object>