I spoke to Daniel last night and he confirmed that Live HTTP Headers, the Firefox extension for web developers is now fully functional on Firefox 4.

You can download it on http://livehttpheaders.mozdev.org/. The version 0.17 is not yet available on addons.mozilla.org. It should available as soon as it is approved by the addons team.

A great thank you to Daniel for his work on this wonderful addon.

UPDATE (2011-05-16): The addon is now available on addons.mozilla.org.