If you have a multitouch trackpad, you may be used to zooming in and out of web pages in your browser. Unfortunately, Firefox 4 disables them by default. Here's how to get them back.
To get back pinch in and out gestures for zooming, just type about:config in your address bar, promise Firefox you'll be careful, then type pinch in the search bar that comes up. Change the following values to match:
browser.gesture.pinch.in cmd_fullZoomReduce browser.gesture.pinch.in.shift cmd_fullZoomReset browser.gesture.pinch.out cmd_fullZoomEnlarge browser.gesture.pinch.out.shift cmd_fullZoomReset
After that, you should see regular pinch-to-zoom functionality comem back to Firefox. I have only been able to test this on a MacBook; so if you other laptop users get it working on your multitouch-capable touchpad, let us know in the comments.
Enable Pinch/Zoom on Firefox 4 [Mac OS X Hints]