If you have installed the Flash plugin but it does not appear in the Add-ons Manager, open about:config and make sure that the preference has not been set to 'false' (if it has, right-click on it and select Reset to set it back to 'true'). Note: On Windows, the Flash plugin is detected via plugin scanning. If the Flash plugin is disabled, click the 'Enable' button to enable the plugin. Firefox 22, SeaMonkey 2.19 and below: Click the 'Disable' button to disable the Flash plugin.Select 'Always Activate' to enable the plugin. Firefox 23, SeaMonkey 2.20 and above: Use the drop-down menu and select 'Never Activate' to disable the plugin.Find the entry for the Flash plugin ('Shockwave Flash' on Windows).Click on 'Plugins' in the left panel of the Add-ons Manager (as shown here).Open the Add-ons Manager by clicking 'Add-ons' in the Firefox (or Tools) menu ('Tools -> Add-ons Manager' in SeaMonkey) or by entering about:addons in the Location (address) bar.Installed plugins, including Flash, can be disabled and enabled in the Add-ons Manager (see Managing installed plugins for details). 6.15 Plugin Check reports outdated Flash has been disabled when the Flash plugin is not installed.6.14 The plugin for this content has been disabled.6.12 Not detected due to disabled plugin scan for PLIDs - Windows.6.5 No audio when Flash video originates from an external site.6.4 Performance or display issues with certain Flash videos.

6.3 Flash player not working on certain websites.

6.2.2 Disabling Protected Mode in Flash 11.3.

6.2.1 Flash Player 11.3 Protected Mode - Windows.

6.2 Flash Protected Mode issues on Windows Vista and above.

4.2.1 Uninstall using Windows Control Panel.

Javascript flash player for firefox