While embedding a SWF in HTML is not too hard, there are a few subtleties for different browsers, detecting if Flash is installed, etc. For enabling AJAX, there are standard
Apple (Link for example)
Content that your plug-ins will view needs to be embedded within HTML. Most browsers do this with an EMBED tag, but others require the OBJECT tag. For maximum compatibility, you can tune your page to support both.
Adobe (Link for example)
The OBJECT tag is used by Internet Explorer on Windows and the EMBED is used by Netscape Navigator (Macintosh and Windows) and Internet Explorer (Macintosh) to direct the browser to load the Macromedia Flash Player. Internet Explorer on Windows uses an ActiveX control to play Macromedia Flash content while all other browser and platform combinations use the Netscape plugin technology to play Macromedia Flash content. This explains the need for two tags.