I am not a web guy but I am a video guy. I am shooting a gentleman in front of a greenscreen so he can magically walk out onto his website and greet people (I think these are called "sprites", no?).
So shooting him and removing greenscreen is no problem, but then what format do I give it to the web guy to preserve the alpha channel? Can I do this in Adobe Flash Encoder? Any help as to the steps in the process would be appreciated. Thank you...
In short words: You can create a Flash movie with your transparent video inside and add a transparent property to the window mode of the swf inside the HTML, then, place the Flash inside an absolute or fixed positioned div.
If you are not familiar with those concepts you may learn them one by one. Writing a full tutorial of the process is way too far for a single post, but you can go step by step and ask if you have any problems.