vertical bars over images in firefox

[Mike Wright]

Hi all,

When using firefox since fc6 (I skipped fc5) I've noticed that many 
images, suchas .swf, now display as a large pair of vertical bars, 
somewhat simalar to the insignia worn by U.S. Army captains, that may 
appear alone or on top of some other background.

On really lousy sites where it's flash or nothing or where most of the 
adverts are flash this is (IMO) just plain ugly and really annoying. 
It's as if someone is threating "Use flash or else we'll destroy your 
user experience".  If that's the case how about a little CSS ala "body 
{display: none;}" and we wouldn't have to waste our time on sites like 
that.  <-- me being facetious ;)   Whatever happened to "failing 
gracefully", the mantra of web designers?

Does anybody know where these abuses have come from?  Are they from the 
Mozilla project or is this something peculiar to fedora's spin of 
firefox or perhaps something peculiar to fedora itself?

Regardless of its origin I would like to stop it.  Anybody know how to 
change this behavior?

Forever indebted to whomever has a solution,
Mike Wright