Thank you for your post.
Open the file in using FileMaker Pro 7 or greater. Pull down the File menu and select Sharing -> Instant Web Publishing. Turn on Instant Web Publishing, highlight the file in the lower left quadrant, and in the lower right quadrant, set the Instant Web Publishing access to All users. Quit FileMaker Pro and open the file again on Server. You should now be able to access this file using Instant Web Publishing.
Let me know if you run into any difficulty.