Go to your address bar and type "about:config", press Enter, in search bar, type "plugin.state.flash", on the option that will appears double click or click with right button mouse and click and "Edit...", then change its value to 0 (never active)

0 <-- Never active.

1 <-- Ask to active.

2 <-- Default, always active.

Does it help if you set the plugins.notifyMissingFlash pref to false on the about:config page?

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

Thanks to both toddy_victor and cor_el for their replies. Went into about:config. set plugin.state.flash = 0, plugins.notifyMissingFlash = false. Still getting messages asking if I wish to download Flash. Format of the "download Flash now" popup window seems to have changed; don't know if that's related.

Here is a test site that always has video content: http://www.bbc.co.uk/news/video_and_audio/

Thats weird try starting firefox in safe mode and do the same changes

Started Firefox in Safe Mode. Changes to about:config are still there:

plugin.state.flash;0 plugins.notifyMissingFlash;false

In Safe Mode, browsing to the test site mentioned in my last post still gives a popup asking to download Flash.

Try go to your plugins page search for flash change its option to never active.

When appers the pop up asking to you install flash, isnt there the checkbox with the option "Dont show it me again"?