Review for Duplicate Tab by ander
Rated 4 out of 5 stars
In FF 3.5, you can open a duplicate tab by holding Ctrl and dragging the tab to an empty place on the tab bar. You can also open the tab in a new window by dragging it into the content area.
Mike DePetris has also released a 3.5-compatible version of this add-on, which you can find on one of the add-on's MozillaZine pages:
http://forums.mozillazine.org/viewtopic.php?f=48&t=83785&start=165
I think he's simply changed the FF version number in its script, but I've installed it and it works great.
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