Do you want to see HTTP headers of different web pages while browsing? If you are a web developer using Firefox 3, then there is an invaluable little add-on for you called Live HTTP Headers. It displays the HTTP headers along with many other information such as debugging cookie, http and server transaction, etc.
You can also use it in optimizing the SEO by verifying 301 and 302 redirects which is very valuable. Tracking and analyzing js-requests is much easier with this add-on.
To add a manual shortcut for Live HTTP Headers go to Views > Toolbars > Customize and drag the add-on to the toolbar.
You can select weather to open LiveHTTPHeaders in a new tab or existing tab, you can also filter out urls among many other options.
Sadly this add-on doesn’t include inline search, copy to clipboard feature, and it lacks the feature for memorizing the last settings, so that you don’t have to reset every time you open this add-on. Overall it’s a great little add-on that you must try if you are a web developer. Enjoy!