Rated 5 out of 5 stars

le blseal ar Lún. 22, 2009 · buan-nasc

Spyder, Lucian, sounds like you're looking for Server Spy (https://addons.mozilla.org/en-US/firefox/addon/2036). Nice little addon, displays the web server type in the status bar, and double-clicking on it displays additional details (like what extensions have been loaded on it).

As for LiveHTTPHeaders, it's the best addon of its type!