Hello. I have searched and tried to solve this for days now and I simply can't figure it out. Firefox version: Mozilla Firefox 31.5.3 ESR Firefox plays a presentation with MP4 video. At first we got this error generally when we tried to play MP4: Video Format or MIME Type is not supported Adding: "AddType video/mp4 .mp4" to the .htaccess file on the server solved that. After this we have been able to play mp4 inside Firefox without any issues. We can even start Firefox from within a script as long as we run this script from the command line or Desktop menu as the standard user. However running the exact same script using crontab for the standard user, again results in the "Video Format or MIME Type is not supported" error. Export display is set and Firefox does open as it should. Youtube videos and everything else in the presentation is working. We simply just can't play MP4 video content. Just as if the .htaccess information is ignored or what ever else could be the cause. Anyone who can explain what the differences between opening Firefox from users crontab and users Terminal console could be in terms of playing MP4 video? Any help is much appreciated. Thanks. Kind Regards, Kevin