1. Install the add-on from the link in Firefox 14 and above.
2. Open the UI for the developer tool "Graphical Timeline" using any of the following method:
a. Ctrl + Shift + Q
b. Tools/App Menu > Web Developer > Timeline
c. Shift + F2 and then click Timeline
3. Click record to start recording events.
4. Have fun :)
PS: for more info, visit http://grssam.com/2012/08/gsoc-comes-to-an-end/
Graphical Timeline. A new Developer Tool for Firefox
addons.mozilla.org