Review for Live HTTP Headers by anthony
Rated 5 out of 5 stars
Follow these steps to make it work on 3.6 RC1 ;-)
http://www.howtogeek.com/howto/8900/firefox-3.6-release-candidate-available-heres-how-to-fix-your-incompatible-extensions/
To create your own collections, you must have a Mozilla Add-ons account.