Background Tabs is a Firefox extension that enables searches from the search bar or entries to the URL bar to open in background tabs by using the [CTRL] key when hitting [ENTER]

DOWNLOAD 0.368 HERE.

Version 0.2 doesn't seem to work for the URL bar in 3.5.7, at least on Kubuntu Linux... the search bar does work... Otherwise, tested on: 3.5.2 (Kubuntu/Shiretoko), doesn't seem to work (yet) on 3.0.*
Older version available for download at addons.mozilla.org
Also see the related, but simpler: Search4Later (which supports FF 3.0.*)

Note how the opened tab is not the dominant tab...

Normally, when you enter something in the search bar or URL bar and hit [ENTER], it replaces the current tab's contents.

If you hold down [ALT] when you hit [ENTER], it will open the contents in a new tab, and it will switch to that tab.

I wanted the additional option of holding [CTRL] when I hit [ENTER] to cause the new tab to be opened but not switched to. This extension accomplishes that.

You can also click the search icon after entering text, and if [CTRL] is down, it will open in the background. This does not work for clicking the "go" icon to the right of the URL bar.

Users used to the IE-style where the [CTRL] causes prefixes/suffixes to be added to the typed-in phrase will notice that functionality gone.

Note that there is a hidden browser preference called "browser.search.openintab". It defaults to false. If you set it to true, then the behavior of this extension stays the same, but the normal [ALT] modification reverses with respect to [ALT], in terms of searches from the search bar.

(The setting available at Preferences->Tabs->"When I open a new tab, switch to it immediately", a.k.a. "brower.tabs.loadInBackground", which affects the behavior of [CTRL]-clicking URLs in pages, may also play into things, but I don't think so...)

Rather related Mozilla bug: https://bugzilla.mozilla.org/show_bug.cgi?id=237027

Possible future features:

• the ability to change which key combinations do what
• the ability to have the default (no key) action be changed as well

Comments/suggestions/bug reports welcome!