Are you wanting to try and use Dropbox to host your application, if so, this is possible just copy your application up to the public area on Dropbox then share the public address to your index.html. I have uploaded the sample flex viewer to my Dropbox account to show it working:
I tried setting up a flexviewer appliction on DropBox but I couldn't get it to work. It always just prompted me to download the index.html file or just showed me all the files in the folder.
