Disclaimer: If you’re visiting this page by link, I’m afraid I’m not the original author of the page you’re looking for. The original content was posted at a page under the “phil.im” domain; when I found the domain had dropped and was (at the time) unregistered I picked it up for personal use (with my name Phil, and all). The Phil.im page drives a little traffic to this site and, rather than give everyone a 404 error I thought you might appreciate some trace of the information you expected to find here.
UPDATE: you can find the original phil.im post at Archive.org.
I’ve taken no effort to test these solutions, but I hope the info helps, and happy (uninterrupted) downloading!
from: https://support.mozilla.org/en-US/questions/906271
• set browser.download.manager.quitBehavior to 2 in about:config
• original source for this solution appears to have been the original phil.im page
from: https://support.mozilla.org/en-US/questions/845991
• set the pref browser.download.manager.quitBehavior to 2 on the about:config page
• see http://kb.mozillazine.org/browser.download.manager.quitBehavior for more info
from: http://www.neowin.net/forum/topic/994228-why-doesnt-firefox-warn-me-im-downloading-stuff-on-close/
• “Personally I use Download StatusBar (not a fan of the extra window), if I have something running and I close the browser, it’ll automatically pop open the download window so downloads don’t get interrupted.”
• “I personally use Download Manager Tweak Firefox extension because I like having the downloads under a tab (I’m weird like that). ”
see also: http://lifehacker.com/5819311/how-to-prevent-yourself-from-accidentally-quitting-firefox-or-chrome