I would like to add: In About:Config, I have this strange entry: Plugin.disabled_full_page_plugin_type and it listed a gazillion application from videos to audios to documents extensions, I reset it to default, it still there but all these applications extensions were removed, and it still won't play any video on Howcast.com, it is killing me! Please note, the attached screen shot was before I reset it to DEFAULT. This entry wasn't there in any previous version of Firefox, this is new and it is possibly causing the problem. I know so for a matter of fact, it wasn't there in any previous version of Firefox for absolute certainty, mainly version 42 and prior versions when streaming played fine.

Howcast streams videos from Ooyala.com as MP4 and H.264, never had a problem playing either one with Firefox except from Howcast.com.

I tried a video from howcast.com and ity played ok. I note it was an HTML5 YouTube video.

In your ordinary configuration look at the page

• https://www.youtube.com/html5

For me that shows all; or all but WebM are available; and the box is checked to use HTML5 when available Does your Firefox show something different ?

Possibly some of your Video related addons are interfering. Next try in safe mode and most of your plugins disabled. Disable FlashPlayer & VLC etc.

I am not using XP at present, and am not sure if that differs from more up to date Windows in its HTML5 handling.. See also:

• HTML5 audio and video in Firefox
• Fix common audio and video issuess_youtube-html5-video-player-issues

If all else fails maybe using flashplaert is a workaround, possibly with the addon https://addons.mozilla.org/firefox/addon/youtube-flash-video-player/

Awesome answer, Kudos, disabling VLC plugin solved the problem on Howcast, wow, I am flabbergasted. P.S. A couple of days ago, the video on MSN.com sites stopped working, mind you with the most up to date Flash Player, disabling it doesn't fix the problem either, this is the message I get: We are sorry, but your browser doesn't support this video, please install Adobe Flash Player version 10 or later. I have NPAPI version 22.0.0.209, the latest version, it works beautifully on all test sites listed on Adobe, what gives? P.S. Resetting Firefox with no add-on didn't do the trick either. Does Microsoft have issue with Firefox, if so, the hell with Microsoft and MSN I say.

Thanks for the reply, glad howcast now works.

MSN I suspect their error message is old and needs updating, it probably is intended to tell you to use a recent Flash player version, not to disable the latest one.

I tried their top video it worked using Flashplayer 22

• http://www.msn.com/en-gb/video/wonder/an-entire-year-of-earth-caught-on-stunning-new-nasa-video/vi-BBuDLu2

But for some reason not with Flash set on click to activate in safe mode or otherwise, and not until I had seen the adverts. Maybe if set to remember the site for FlashPlayer it would always play, but I did not test that.

You do apparently have FlashPlayer 22 installed on Firefox. Maybe you have a script blocker the site objects to, or maybe once again it is one of your other video players interfering. See also

• Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems
• Flash Plugin - Keep it up to date and troubleshoot problems
• Presumably all other FlashPlayer video sites are ok it is always a sensible idea to check on the Adoble test page to see what your browser is actually using http://www.adobe.com/software/flash/about/ (Be aware of potentially unwanted downloads they will push from that page including on installs)

Only the first video (by Adele) plays fine on MSN site you listed as long as Adguard and Tampermonkey are disabled, all the other videos won't. There must be a glitch with MSN script, I get Buffer Overflow when tracing the activities of Firefox on MSN, which might be normal though. I changed a million things and non helped, it is not an issue because I have I.E. Rendering Engine add-on to Firefox and when I switch to I.E. it plays fine. I am not into MSN all that much either, no need to waste any further time, I submitted a complain to MSN. Thanks a trillion.

It definitely has to do with Microsoft punishing Windows XP users for not upgrading, same portable Chromium browser plays MSN.com videos on Windows 7 but not on Windows XP. The only problem, Windows 7 sucks, never used it except few times, I am sticking with XP. I got the message loud and clear, no biggie. Other than that, Firefox passed all Flash Player tests on Adobe site. Case closed, thanks a million.

MSN fixed its videos issue, same is true with Howcast, now both play fine on all three browsers without having to disable any plugin. Complaining to the sites administrators seem to have done the job. MSN is notorious for being anti-non Microsoft browsers, unfortunately for Microsoft, it lost a huge share of its browser market, notably after refusing to upgrade Windows XP Internet Explorer.