Are you talking about the video near the top of the screen? I had to wait until the entire clip was downloaded before it played.

Yes! I am talking about the same. It is simply showing a cross on the screen with the message as stated above.

Are you having a problem anywhere else?

Nopes! Till now I have not seen the same problem in any other site. It may be because of the reason that other sites contain .mp4 , .mpg and so on..

That is a problem with the HTML5 media player that plays the file via the video tag. If you do not have the required codec installed to play the video then you see this error message.

This is an MP4 video:

• https://mlxstorage.blob.core.windows.net/mec-v2/MECIntroVideo.mp4

• https://developer.mozilla.org/Apps/Build/Audio_and_video_delivery
• https://developer.mozilla.org/HTML/Supported_media_formats

What should I do now?

Another one that works only with Safari. Beginning to get tiresome.

Note that the OP is using Windows XP. On Windows XP you may not have support for MP4 installed like Vista and later have as part of Windows Media Foundation.

Do you otherwise have problems with playing media files with the built-in HTML5 media player?

Also make sure that this pref is set to true on the about:config page.

• media.directshow.enabled = true

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

I have no problem playing other HTML5 videos. I did not have that setting in about:config. I added it, but that did not help.

Yes the about config setting is set to be true only! I am not facing problem anywhere else with the built-in HTML5 media player.