Yesterday, we talked about the Google code to enhance the 404 experience. A number of issues were reported with the code in the Google Groups announcement thread, and Google has fortunately made tweaks to fix the issues.
Google representative JohnMu says that you should be returning a 404 error when using this widget (though it will now work if the page returns a 200 status too!) That's great, because in the example in yesterday's blog post, it wasn't working because a 404 wasn't being returned. Try the advertize.html page now and let us know what you think.
Forum discussion continues at Google Groups.