If you have seen this when visiting sites it is likely not the sites, but an error in the code of your virus/spyware checker. It is reading part of the embed code as malware - something harmful.
In this post, the person claims to have spoken with YouTube and Google and it is not a legitimate virus, but an error.
In any event, I have removed embedded videos from my front page for the time being.
False alarm: Actns/Swif.T Virus in embedded Youtube videos?
Actns/Swif.T virus affecting embedded YouTube vids?
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The obedient are not held captive by Holy Mother Church; it is the disobedient who are held captive by the world!