The Macromedia Flash Player is not installed on your computer:
This is the software that “plugs-in” to your browser and allows content written in Flash to be displayed. This product requires Flash Player 7 or higher, but it does work with some later versions of Flash Player 6. You can download the latest version from Macromedia.com using the link.
Pop-up blockers also block the Flash Player:
Pop-up advertisements are a serious irritation to many people who now use pop-up blocking software to counter the problem. This may also prevent the Flash movie from displaying if the blocker specifically targets Flash content.
Security settings are too high:
If you are viewing the Flash movie on your school network, it may not play because your system administrator has changed the security settings to ‘high'.