Use Internet Explorer to be able to view transparent Flash Content. For the transparency effect to work as desired, don't add a filler background element to your movies.
Many developers add a large, white rectangular box, etc. to simulate white color.
Make sure the drawing area behind the main movie is clear of any unwanted colors, etc. I hope the above information helped. If you have any questions or comments regarding this information or anything Flash related, please don't hesitate to contact me. I try to have all email inquiries replied to within 4-12 hours. Inc. All Rights Reserved.