My Add Old Browser Message Dreamweaver extension has received Macromedia approval. There were some small changes to the extension interface so, although the code it inserts is the same and the old version won’t do anything evil to your copy of Dreamweaver, you might want to grab the new copy at the Macromedia Exchange.
The extension will add a message viewable only to users of older non W3C DOM supporting browsers telling them that although they can see your content the site is not designed for their legacy browsing software.