Guideline 8. Ensure direct accessibility of embedded user interfaces.
Section 508, (Technical Standards) 1194.22
http://www.w3.org/TR/WCAG10/#gl-own-interface
"Ensure that the user interface follows principles of accessible design: device-independent access to functionality, keyboard operability, self-voicing, etc."
8.1 Make programmatic elements such as scripts and applets directly accessible or compatible with assistive technologies.
Nothing is more annoying than going to a website and being presented with some fancy flash introduction that doesn't give you the option to skip it. It's like having to read the FBI warning every time you pop in a DVD, and no matter which buttons on the remote you press, you can't skip it. My time is money, and I can't afford to waste precious minutes on something that I should be able to skip with a simple click of a mouse. This is where guideline 8 comes to the rescue.
When implementing scripts into your web page, give users the option to disable the script inside the page itself, without having to go into the browser preferences. You can do this by providing either a link or a control panel on the page. When implementing applets, make sure that a control panel is provided in the applet window to allow the user control over the applet. For example, when embedding videos into web pages, give the user a control interface to pause, stop, rewind, fast-forward and play the video. Also, as a personal favor to me, please do not make your videos autostart. Show your user that a video is available, and if they want, they can view it. This will help conserve your bandwidth and will help to avoid loud sounds coming from your computer in the middle of a teacher's lecture (You didn't hear this from me).
In Conclusion, be responsible, follow the guidelines, make your sites user-friendly and accessible to all.