Actually just found this on the Mozilla site which seems to work though haven't tested it thoroughly yet. I had to add the trailing slash to the Param tags to get it to validate. [forums.mozillazine.org...]
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"
codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,40,0"
width="600" height="450">
<param name="movie" value="test.swf" />
<param name="quality" value="high" />
<!--[if!IE]> <-->
<object data="test.swf"
width="600" height="450" type="application/x-shockwave-flash">
<param name="quality" value="high" />
FAIL: (the browser should render some flash content, not this).
</object>
<!--> <![endif]-->
</object>
