Check your plugins are updated!

• https://www.mozilla.org/en-US/plugincheck/

Disable the quick time and give a try

Hi thanks for your reply.my firefox does not have a quicktime plugin and all my plugins are updated.so the problem is still reoccurring. Any other solutions? Additional info: Usually when i click on the download link it would ask if it want to be saved but now it goes to the error page..

Make use of Firefox Addons - Video downloader

• Addons.mozilla.org

Sorry just wondering how it would help in solving the problem. The file is through a direct download link. When clicking on the link there will be a pop-up to where the file wants to be saved (last time) but now it tries to play the video but cant and gives the message.here is a how the message looks like.Like i say before a few days ago it was okay.but i havent been downloading for the pass few days but when i tired yesterday, i cant

You should still be able to save the video via "Firefox/File > Save Page as" or possibly via the right-click context menu.

• bug 835381 - Matroska MKV video files are not WebM - don't try to play them

(please do not comment in bug reports: https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)

Thanks for the info. It helped a lot.