Today I needed to view the HTTP headers of requests I made with Mozilla Firefox. Recently I updated to Firefox 2.0 by uninstalling the old version, and installing Mozilla Firefox fresh. Hence I had to reinstall the extensions I use a lot, the most required one was Flashblock. Surfing one day without made it clear to me what I had been missing for a long time: annoying animated advertisements.
However the extension I needed to install today, Live HTTP Headers, wasn't available for version 2.0 of Firefox (yet) so I had to hack the XPI file.