Input box - Media Dir URL
Here you enter the full http path where your files are stored. (Don't use spaces!) For example: http://dl.dropbox.com/u/1234567/Chinese/
When you download your deck from your device, the app will look to this location for your media files, rather than on my server.
If you update an existing deck, you don't need to enter this value again, as the app will remember the old Media Directory used with the deck.
Google Docs for text
If you are using Google Docs as the source of your text data, I recommend you store your media files in Dropbox rather than in Google Docs, especially if you have a lot of files. You tell the app where to find your media files by adding a special header row to your text (at the very top). For example:
* media-dir http://dl.dropbox.com/u/1234567/Chinese/
These go in columns A, B and C (the space between represents a new column, or tab).
Dropbox for text
If you use Dropbox to store your text files, then you don't need to use this Media Directory feature. See the Dropbox instructions on the main page for details on how to use private directory storage.