hopefully we've seen the last of chromeless windows, it was just exploiting a security flaw in internet explorer that microsoft have now patched (at last, I hate the things )
it could be what you saw was a transparent flash movie, these have been available (using activeX) on internet explorer on windows for quite a while, but now the latest flash player adds support for netscape/mozilla based browsers on windows and some browsers on a mac running OSX. You can layer the transparent movie over the page, here's a link,

http://www.macromedia.com/support/fl...ents/wmode.htm

you can put your object and embed tags from the movie you make within a div (or some other html holder) that allows you to layer content, eg

<div id="myFlash" style="z-index: 2; position: absolute; left: 50px; top: 10px;"><object .....

</object>
</div>