In order to watch Yahoo!7 videos using Fire Fox, you will need to configure the browser correctly.

Limited Functionality watching Yahoo!7 Video with Fire Fox –

Yahoo delivers video formatted in Window Media, Flash, and QuickTime. The majority of our content is formatted in Windows Media. For content formatted in Flash or QuickTime, all video playback functionality is supported. However, Fire Fox (and all Mozilla-based browsers) do not support the Active X scripts needed to control video playback. Therefore, the video player controls (pause, fast forward, and stop) are disabled for videos formatted in Windows Media using the Fire Fox browser.

Yahoo will continue to work to improve the video experience using the Fire Fox browser.