It's one way Safari stays a bit 'faster' than other browsers. Full refreshes are time stamped... eventually Safari will load the new banter even if you do nothing... BUT... Safari doesn't figure the 'banner' changes very often on webpages, (which is true), so it time stamps the last full refresh so that clicking refresh doesn't actually completely reload the page.
Other browsers do the same but they do a complete reload of the website more often.
