I have this html5 code, with a MP4 for Chrome (working), an OGG for Firefox (failing) and the same ogg via a java applet for Internet Explorer (working):
<video width="848" height="480" controls="controls" autoplay="true"
<source src="vernissage_cpal_2009.mp4" type="video/mp4" /
<source src="vernissage_cpal_2009.ogv" type="video/ogg" /
<applet code="com.fluendo.player.Cortado.class" archive="http://theora.org/cortado.jar" width="848" height="480"
<param name="url" value="vernissage_cpal_2009.ogv" /
</applet
</video
Firefox display a gray box with a X inside it. The file "vernissage_cpal_2009.ogv" also plays well inside normal media player, like VLC.