I can think of two things that might cause this. First, if a web site's scripts only look at the first digit of the version number, 1 appears to be lower than 9. Such sites should fix their scripts. The second is if you have disabled JavaScript (either globally or for a domain relevant to that site), you may get erroneous messages about plugins not starting, which is because the script didn't run at all.

Can you provide a link to a site or two that has this problem? (Family friendly sites only.)

It's not when I'm going to any sites, it pops up when I go to open my mail. I checked Java and it's enabled.

Are you reading your mail in Firefox (e.g., Gmail, Yahoo! mail, Hotmail) or Thunderbird?

Yahoo

Check out this related question for more information: Why do I get a popup message about Flash?

Sounds that someone updated the JavaScript code on that site and used old browser and Flash detection code for Firefox.

Can you post links to the JavaScript files files used?

You can search for useragent and flash.

• https://www.squarefree.com/bookmarklets/webdevel.html#view_scripts

For Yahoo mail, see reply from Cww for an explanation and workaround in this post --> https://support.mozilla.org/en-US/questions/924230#answer-323590

Same explanation may apply to other sites not recognizing your installed version of Flash (Add-ons > Plugins > "Shockwave Flash" version); for a workaround, contact the site.

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