What do I do if Youtube videos are replaced with "Plugin Blocked"
Youtube video is replaced with a black box and the words "Plugin Blocked" in Safari or Firefox.
This can also occur in other Flash based applications
Update Adobe Flash player on the computer from adobe.com.
Safari and Firefox are blocking out of date Flash Player plugin.
Can apply to any browser on any OS that is attempting to play flash video. Appearance or message may be different on different platforms.