Favorite and useful firefox about:config tweaks [closed]

Question

What is your favorite and most useful about:config tweak ?

My Favorite :

browser.ctrlTab.previews [Boolean] - A new feature of Firefox 3.6, and disabled by default, if enabled (set to true) then you can use the enhanced tab switching capabilities of Firefox. See the Tabbed Browsing area of the Features, Tips & Tricks section for full details.

browser.allTabs.previews [Boolean] - A new feature of Firefox 3.6, and disabled by default, if enabled (set to True) then a new button will be shown at the far right of the tab bar. Clicking this button will open the enhanced tab switcher. See the Tabbed Browsing area of the Features, Tips & Tricks section for details.

Answer 1

I realy love :

extensions.dta.maxchunks

when you donwload DownThemAll Extension it can increase chunk to increase download speed and it's very useful for me.

I usually set it to 100.

Answer 2

browser.link.open_newwindow.restriction [Integer] - This setting determines how new windows launched by javascript (usually popups) are treated. If set to 0, all such windows are opened as tabs in the current window; if set to 1 they open as new windows; and if set to 2 javascript windows will be treated like any other opened link unless they have strict values set.