Does the setting here toggle the warning off?

orange Firefox button or classic Tools menu > Options > Tabs > "Warn me when closing multiple tabs"

Edit: Per the below, the answer to my question is "no it doesn't." While there will be an about:config preference in Firefox 18, until then, the only proven workaround appears to be the Tab Mix Plus extension.

That is a change (bug) in Firefox 16 to ask for confirmation that you can consider as a regression.
There is currently no way to disable that confirmation request.

• bug 772319 - No option to disable the "Close other tabs" prompt
• bug 277079 - "Close other tabs" should always warn about closing multiple tabs

(please do not comment in bug reports)

This is sooo annoying! Please fix it soon. There are loads of upgrades for things far less retrograde than this.

I've just read the bug sheet and I do have to concur with the comments there. I want a browser that works not one that asks for confirmations of the slightest thing. What is the point of being able to disable the warning of closing multiple tabs under the options menu if it does nothing in reality. Remember all the jokes about if Microsoft made cars - emergency stop; "are you sure you want to stop - press the brake again to confirm" sort of stuff - now Firefox is taking that on. For serious users Firefox is becoming third division, and unusable. Please we do like it, but don't make it a "Nappy" (Diaper) browser aimed totally at newbies and kids - or please don't forget to turn the lights off when your final user leaves.

Current Firefox versions have a browser.tabs.warnOnCloseOtherTabs pref that you can set to false to suppress this confirmation.

• http://kb.mozillazine.org/about:config

It should suppress confirmation BUT it doesn't. It still asks every time you "close other tabs", That is the whole point of everyone's gripes.

Thanks, cor-el. The about:config suggestion worked perfectly.

Thanks also for your voluminous contributions to this forum. I imagine a lot of the time it goes unappreciated.