Rated 4 out of 5 stars
In its time, this was one of the best and user-friendly http headers viewer showing timeline of requests with ability to select each request, along with info (separate tab) on cookies, query strings, post data, and content received.
I realise you could do similar with the in-built dev toolbar now, but it's no where near as well laid-out or user-friendly as this great addon was!
As a result, I still use this - I just wish the developer kept it updated and developed it further.
Thank you Martin for your work on this, it has greatly helped me countless times in the past.