@Stomme poes…
Chrome -> Developer > Developer Tools > Timeline
it’s showing blank for me too
This is one of the best articles on using CSS sprites I know of: http://www.alistapart.com/articles/sprites
Though I would say that I’ve actually encountered similar issues with my portfolio where I wanted screenshot’s to only load when their required (scripting free) rather than loading everything in one go (which takes a long time if you have a lot of images going in the page). I’ve been taking advantage of the target pseudo to only add the background as and when the fragment anchor is called (thereby eliminating the issue of heavy initial loads). The morel from my tale is that it depends as to where the background is referenced as to whether it’ll load in the cascade order or whether it’ll load or manipulate the image upon a pseudo event like hover or target 
for any1 who wants to know the time at which a request for a file is sent etc.
Chrome: Tools -> Developer Tools -> Network (in the right side, it shows timeline)
Firefox: Use Firebug add-on -> Net
…continued from earlier post,
Opera: Tools -> Advanced -> Opera Dragonfly -> Network
Safari: Settings -> Preferences -> Advanced Tab -> Show Develop menu in menu bar(Select this option. Now in the menu bar, there’ll be a new item - Develop)
Develop -> Show Web Inspector -> Resources