its actually to do with the number of HTTP(havent tested with ftp) connections safari will make at once. if you're loading a page, Safari will make 4 connections to the server until all the files needed for the page are loaded. if you're downloading something, and start loading a page, it will use 3 connections for the page, because 1 is being used by the download. you might find something by playing around with something like Safari Enhancer and/or the debug menu..