It is possible to do. Maybe your css is just targeting the wrong object? Here's some sample code of mine, using a div. The name of the swf is intro2.swf. I'll make the class name of the div "container":
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#container {
margin:0 auto;
position:relative;
text-align:left;
clear:left;
}
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Then, in your html, add the following:
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<div id="container">
<object classid="clsid
27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=9,0,28,0" width="800" height="750">
<param name="movie" value="intro2.swf" />
<param name="quality" value="high" />
<embed src="intro2.swf" quality="high" pluginspage="http://www.adobe.com/shockwave/download/download.cgi?P1_Prod_Version=ShockwaveFlash" type="application/x-shockwave-flash" width="800" height="750"></embed>
</object>
</div>
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Substitute your swf name for intro2.swf, add whichever css properties you'd like, and the appropriate width/height, and you should be good to go. Also, make sure that your paths are correct.
-Lou