Všetky odpovede (2)
Please explain the problem in detail. What happens? What is/are the exact error message(s) ?
Firefox relies on built-in OS support to play media files via the HTML5 media player. On the Windows XP platform you do not have native support for playing MP4 files with the HTML5 media player.
You can try if the solution posted here to add support for playing MP4 files works for you.