How to remove "Additional Plugins Required..." alert from Firefox

I'm not a Flash user, in fact, I uninstalled flash from my Mac using this link. The problem now is that Firefox always alerts about "Additional Plugins Required..." every time I visit a site with embeded Flash. Is there some way that I can disable this alert message?

I'm using Firefox latest beta (4.0b6)

Thanks!

From superuser

• One simple way to disable the yellow warning bar asking you to install additional plugin is to type about:config in the Firefox address bar.

  At the filter bar, type plugin.default_plugin_disabled and press enter. You should see that the value for this name is true. Double click on this item to change the value to false.

  Takes effect immediately without restarting the browser.

  source

  licorna : Don't know if it is because I have Firefox 4.0b6 but I had to change **plugins.hide_infobar_for_missing_plugin** to **true**. Anyways, your answer led me to the correct one! Thanks.