14 DAY TRIAL // Although a stable release for Firebug has already been issued (and it comes with a slew of new stuff), the developer already has the next version for the Firefox extension in the oven.
As far as the specs for Firebug 1.10 are concerned, there are no public details yet, but the one sure thing is that it should expand the compatibility table. The stable release of the extension is now compatible with Firefox 6 through 11. For lower versions of Firefox you should use version 1.7.3 of the extension.
Firebug 1.10 should show up this week in alpha stage of development. It is designed to work with Firefox 12, nightly versions. However, until its release you can use Firebug 1.9.0b6, available here.
You can download the latest stable version of Firebug from this link