You can run it any time from HostTracker main page for free - and it really helps to see how your website performs from different countries and find its weak spots, if there are any. Let us check what we see there, if we test google.com:
Top line shows us basics about the loaded page: how many http requests have been made to complete it, if all of them were successful, its size and load time.
The first box out of three below this line represents the real look of the page during loading. You can see there a series of images, each one corresponds to a specific time during page execution. So, if some elements are downloaded too slowly or some scripts are not executed properly - you can notice it there, just like in your own browser. With one huge difference - you can make this check for many locations and different device types in few seconds! Two other boxes contain graphs of single core CPU usage and memory usage by a browser while the page is loaded.