Assume that I\'ve fired up Firefox with Firebug enabled on a random site (say slashdot.org). After loading the site I start editing the page using the Firebug > HTM
You can configure an external editor. Open firebug, on the left you have firebug icon, press it and click open in editor and then configure editors. It works with Gedit and Bluefish.
To configure gedit: open FireBug's configure editor and click add, name it gedit and then browse for the executable within 'usr/bin' and select or type in gedit. You can test the configura before saving.