Was browsing the MyIE2 forums and found a link to the ieHTTPHeaders plug-in — a plug-in that shows the HTTP and HTTPS headers that are exchanged between whatever web server you’re talking with and your browser. Nice! I’ve used curl and Microsoft’s wFetch which is included in the IIS 6.0 toolkit (see MSKB 284285 for details) but having it integrated into the browser helpls a lot.
BTW, Jonas Blunck (ieHTTPHeaders author) has some interesting tools and links on his site.