How I got firebug back after updating to Firefox 4.0 on Ubuntu
After following these clear instructions for upgrading to Firefox 4.0 on Ubuntu 10.04/10.10, after delighting in the speed and reveling in the speed and other good stuff, I wanted to get firebug back so I could do some socially useful work!
So I went to Tools / Add Ons from the browser menu, and a pop-up window showed me all my disabled stuff that was incompatible with Firefox 4.0
Then, I returned to Add-ons Manager at Tools / Add-ons and from the little drop down list icon to the left of the search box in the top-right corner, I selected Install Add-on from File...
I was told Firebug would be installed after restart, and it was. After enabling the Add-on bar from View / Toolbars, there was my beloved little bug in the bottom right hand corner where it belonged. A screamingly fast firebug for the screamingly fast Firefox 4.0!
And that's how I got my Firebug back! Lots of new features for 1.7.1 also!