swfobject

Flashobject is a small Javascript file used for embedding Adobe Flash content.
The script can detect the Flash plugin in all major web browsers (on Mac and PC) and is designed to make embedding Flash movies as easy as possible.

It is also very search engine friendly, degrades gracefully, can be used in valid HTML and XHTML 1.0 documents, and is forward compatible, so it should work for years to come.

<script type=”text/javascript”>
 // <![CDATA[
 var so = new SWFObject("sample.swf", "sotester", "100%", "100%", "9.0.115", "#000000");
 so.useExpressInstall('js/expressinstall.swf');
 so.addParam("scale", "noscale");
 so.addParam("menu", "false");
 so.addParam("allowScriptAccess", "always");
 so.addParam("allowFullscreen", "true");
 so.write("flashcontent");
 // ]]>
</script>

you can download the latest version from : http://code.google.com/p/swfobject/ 
this good script is from: http://blog.deconcept.com/swfobject/