Another new feature that made it into Firebug 1.6a14 (available later today) is tracking HTTP responses coming directly from Firefox BFCache (back/forward cache) and displaying them within the Net panel.
The purpose of this cache (note that this is different from the standard HTTP cache) is to make navigation in the browser history fast.
The consequence of using the BFCache is that there is no HTTP activity (that's why it's fast) and so, till now these requests wasn't displayed in the Net panel.
While I think it was actually correct (since purpose of the Net panel is to monitor HTTP activity), it was confusing sometimes as the Net pane was empty even if it was quite obvious that there need to be some requests.
So, the feature is optional (on by default).
All responses coming from the BFCache are displayed in gray. See the next screen-shot that shows what happened when I pressed the Back button.
One thing I am still not sure about is whether the gray color is enough to distinguish BFCache responses from regular HTTP responses...
Another way how to differentiate these two different responses is depicted here (just a mock-up):
BFCache response could be hidden behind an extra entry that clearly depicts that it's BFCache related. This would make the Timeline column a bit hard to read since there would be empty rows in the waterfall diagram, but perhaps nobody is interested in that if it doesn't come from the server and there is not HTTP communication anyway.
What do you think?
Any tips how to cut the Gordian knot?