Comment 48 for bug 481541

I knew this was coming...as soon as I logged into Hotmail today with the new
Aviary with this patch checked in, I knew someone was going to say that they
like clicking all their email links first, and then going through them after
they close out their external email program (Hotmail made me consider this, in
this case, only because it ALSO uses diverted links (by way of Javascript) to
popup the URLs inside your emails into new windows, and the fix of this bug
controls the action of BOTH external programs AND these javascript popups). For
Hotmail's case, you can't middle click on the links because Bug 55696 (and Bug
125668) hasn't been fixed. In the case of external email programs, obviously,
you can't apply the middle click functionality to links within them AT ALL.

So, if you ARE still talking about a TAB focus problem, which this bug fixes,
but which I doubt is your problem, then read up, and you will see that
browser.tabs.loadDivertedInBackground is the setting that you need to fool with.

More likely, you are not talking about the TAB focus problem that this bug
fixed, but instead referring to a WINDOW focus bug, where the entire Firefox
WINDOW gains focus for each link clicked in an external program. Well, that is
a whole 'nother problem. This bug did not change that behavior one way or the
other. If you clicked on an external program link before this bug was fixed,
the Firefox WINDOW WOULD still gain focus; the whole problem here was that the
TAB associated with the link wouldn't.

A way to fix YOUR problem, which seems to be next on the list of focus bugs, is
to have a new option added to the Firefox View menu called "Never on top" that
you could select before you read your mail, and/or have an option added to
Firefox that controls whether or not the entire window steals focus when
external links are clicked. I don't think there is an enhancement request for
either of these. In your special case of using Thunderbird though, I assume you
CAN middle click on links within emails and have them open in Firefox tabs? In
this case, Thunderbird should still be treated as an external program, and so
the way of doing things before was buggy behavior, though you sure thought it
was a feature :)

To sum this all up, most likely, this is not the bug you are looking for, though
the title makes it sound like it is. Instead, you have to understand that your
previous convenience was actually just a coincidence and buggy behavior, and the
correct way of implementing what YOU are wanting still needs to be come up with.