Understanding Firebug's Net Panel

I am trying to get a hang on analysing the performance of a web page using Firebug's Net panel. The following screenshot shows an example of a google query. For the sake of this di

Solution 1:

1. The response of the first request needs to be parsed to find out what else needs to be loaded. This parsing time causes the gap to the second request. See also my answer to a related question.

2. Responses coming from cache still have an associated network request, which returns the 304 HTTP status code. You can see the request and response headers as well as the response headers of the cached response when you expand the request. In contrast to that there is also a response that is directly served from a special cache called Back-Forward Cache (or BFCache). These responses happen directly after the browser start when you have the option enabled to restore your tabs from the last session and also when you navigate back and forth in the tab history.

3. This depends on the network connection speed and the response's size in the first place but also on how long the server takes to send the full response. Why that one request takes that long in comparison to the others can't be explained without knowing what happens on the server side.

4. The load event is fired when the page request is loaded including all its depending resources like CSS, images, JavaScript sources, etc. Requests initiated after the load event are loaded asyncronously, e.g. through an XMLHttpRequest or the defer attribute of the element.