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Google Mobile Blog gives another reason why the mobile homepage will load faster: "when you navigate to google.com in your browser, we cache the homepage on your phone. If you bookmark this homepage, then returning to Google using the bookmark is almost instantaneous."
Since the homepage is now static and doesn't display personalized content, it can be cached indefinitely. Google chose to politely ask your browser to cache it for 1,209,600 seconds = 14 days.
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But Google still wants to see how many people visit the mobile homepage and this is impossible if all the content is cached. That's why, the last element from the homepage is a tracking pixel, a 1x1 GIF image: http://www.google.com/m/ping?source=magmahome.