Guideline 7. Ensure user control of time-sensitive content changes.

This is the guideline that I did my presentation on, so while I'm no expert I do remeber some basic points. The screen readers, or user agents, may not have the capability yet to disable moving text or flickering content. So make sure develop the website following these guidelines so its easily accessible for all users. Plus movement on the page may become such a distraction from the rest of the page as to make it entirely unreadable/usable. 7.1 is a priority 1, the rest are priority 2.

Until user agents allow users to control flickering, avoid causing the screen to flicker. Also note that people with photosensitive epilepsy can have seizures triggered by flickering or flashing in the 4 to 59 flashes per second range!
7.2 avoid causing content to blink (i.e., change presentation at a regular rate, such as turning on and off).
7.3 Avoid movement in pages, so when a page includes moving content, provide a mechanism within a script or applet to allow users to freeze motion or updates. Using style sheets with scripting to create movement allows users to turn off or override the effect more easily.
7.4 Do not create periodically auto-refreshing pages. For example, in HTML, don't cause pages to auto-refresh with "HTTP-EQUIV=refresh" until user agents allow users to turn off the feature.
7.5 Do not use markup to redirect pages automatically. Instead, configure the server to perform redirects.

The BLINK and MARQUEE elements are not defined in any W3C HTML specification and should not be used.

Source: http://www.w3.org/TR/WCAG10/#gl-movement