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• Plugins > Shockwave flash > Change to "Always Active"

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You should see a notification icon in the address bar, but it isn't there to torment you — it should just sit there quietly and you should feel free to ignore it if you don't want to run Flash.

If you are getting more intrusive or demanding messages (e.g., pop-up dialog, infobar sliding down), maybe those could be turned off. Are there particular sites that cause this problem that you could provide a link to?

What I get is an infobar. Here's an example: http://www.adslzone.net/article13583-ejecuta-aplicaciones-windows-en-linux-con-crossover-13.html As I said before, this isn't always the case. I forgot to tell that I set firefox to keep cookies until I close the browser. I don't know if this happens only with flash. I attached an image of the website.

Here's my understanding of what's happening.

When a page uses Flash and there is a visible instance of the plugin (such as a black rectangle where Flash plays, then the infobar is hidden. However, if the page uses Flash and it is not visible in the page, then the infobar is displayed. (Based on comments in this bug: https://bugzilla.mozilla.org/show_bug.cgi?id=942860)

There seems to be a problem in your example, in that the Flash ads on the page are visible to the human eye, but the code deciding whether to show the infobar doesn't see them, perhaps because they are in separate documents loaded in <iframe> elements that are not considered part of the page. That's speculation on my part.

You can use a custom style rule to prevent that bar from ever showing if you like. An example is given in a comment on a different bug: https://bugzilla.mozilla.org/show_bug.cgi?id=950734#c9. If you want to set that up and you're not familiar with userChrome.css, the steps are described in more detail in a couple posts in this thread: https://support.mozilla.org/en-US/que.../979232#answer-507464.

Reading the comments of the second bug report I found this add-on that makes the infobar not to be shown: https://addons.mozilla.org/en-US/firefox/addon/hide-plugin-notifications/ However I'm gonna try your solution. Thanks for the help!