var result = element.autobuffer; element.autobuffer = value;
The autobuffer method buffers the audio or video element to prepare for playback. The autobuffer attribute indicates that the media element is likely to be used, even though it does not have an autoplay attribute. This attribute is ignored if autoplay is present. Buffering the media can improve responsiveness when the element is finally played.
Microsoft Developer Network: [Windows Internet Explorer API reference Article]