New Page Info window
As part of Google Summer of Code in 2006 student Florian Queze set out to enhance Page Info window. Yesterday the code for the new Page Info window landed on the trunk. This means that if will be part of Firefox 3 when it comes out.
The Page Info window is the window you get when you right-click on a page and select View Page Info.
For those who are interested in more info read the bug report.